diff --git a/frontend/package.json b/frontend/package.json
index c490d33..e903838 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -15,7 +15,6 @@
     "@js-temporal/polyfill": "^0.4.4",
     "@microsoft/microsoft-graph-client": "^3.0.5",
     "accept-language": "^3.0.18",
-    "dayjs": "^1.11.7",
     "gapi-script": "^1.2.0",
     "goober": "^2.1.13",
     "hue-map": "^1.0.0",
diff --git a/frontend/src/components/CalendarField/CalendarField.tsx b/frontend/src/components/CalendarField/CalendarField.tsx
index 919614a..58e9286 100644
--- a/frontend/src/components/CalendarField/CalendarField.tsx
+++ b/frontend/src/components/CalendarField/CalendarField.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useState } from 'react'
 import { FieldValues, useController, UseControllerProps } from 'react-hook-form'
 import { useTranslation } from 'react-i18next'
+import { Temporal } from '@js-temporal/polyfill'
 
 import { Description, Label, Wrapper } from '/src/components/Field/Field'
 import ToggleField from '/src/components/ToggleField/ToggleField'
@@ -27,7 +28,7 @@ const CalendarField = <TValues extends FieldValues>({
   const [innerValue, setInnerValue] = useState({
     specific: [],
     week: [],
-  } satisfies Record<typeof type, string[]>)
+  } satisfies Record<typeof type, Temporal.PlainDate[]>)
 
   useEffect(() => {
     setInnerValue({ ...innerValue, [type]: field.value })
diff --git a/frontend/src/components/CalendarField/components/Month/Month.tsx b/frontend/src/components/CalendarField/components/Month/Month.tsx
index 1b25487..e518abe 100644
--- a/frontend/src/components/CalendarField/components/Month/Month.tsx
+++ b/frontend/src/components/CalendarField/components/Month/Month.tsx
@@ -1,34 +1,29 @@
-import { useCallback, useEffect, useRef, useState } from 'react'
+import { useCallback, useMemo, useRef, useState } from 'react'
 import { rotateArray } from '@giraugh/tools'
-import { Dayjs } from 'dayjs'
+import { Temporal } from '@js-temporal/polyfill'
 import { ChevronLeft, ChevronRight } from 'lucide-react'
 
 import Button from '/src/components/Button/Button'
-import { useDayjs } from '/src/config/dayjs'
 import { useTranslation } from '/src/i18n/client'
 import { useStore } from '/src/stores'
 import useSettingsStore from '/src/stores/settingsStore'
-import { makeClass } from '/src/utils'
+import { getWeekdayNames, makeClass } from '/src/utils'
 
 import styles from './Month.module.scss'
 
 interface MonthProps {
-  /** Array of dates in `DDMMYYYY` format */
+  /** Stringified PlainDate `YYYY-MM-DD` */
   value: string[]
   onChange: (value: string[]) => void
 }
 
 const Month = ({ value, onChange }: MonthProps) => {
-  const { t } = useTranslation('home')
-  const dayjs = useDayjs()
+  const { t, i18n } = useTranslation('home')
 
-  const weekStart = useStore(useSettingsStore, state => state.weekStart) ?? 0
+  const weekStart = useStore(useSettingsStore, state => state.weekStart) ?? 1
 
-  const [page, setPage] = useState({
-    month: dayjs().month(),
-    year: dayjs().year(),
-  })
-  const [dates, setDates] = useState(calculateMonth(dayjs().month(page.month).year(page.year), weekStart))
+  const [page, setPage] = useState<Temporal.PlainYearMonth>(Temporal.Now.plainDateISO().toPlainYearMonth())
+  const dates = useMemo(() => calculateMonth(page, weekStart), [page, weekStart])
 
   // Ref and state required to rerender but also access static version in callbacks
   const selectingRef = useRef<string[]>([])
@@ -41,12 +36,6 @@ const Month = ({ value, onChange }: MonthProps) => {
   const startPos = useRef({ x: 0, y: 0 })
   const mode = useRef<'add' | 'remove'>()
 
-  // Update month view
-  useEffect(() => {
-    dayjs.updateLocale(dayjs.locale(), { weekStart })
-    setDates(calculateMonth(dayjs().month(page.month).year(page.year), weekStart))
-  }, [weekStart, page])
-
   const handleFinishSelection = useCallback(() => {
     if (mode.current === 'add') {
       onChange([...value, ...selectingRef.current])
@@ -60,31 +49,19 @@ const Month = ({ value, onChange }: MonthProps) => {
     <div className={styles.header}>
       <Button
         title={t<string>('form.dates.tooltips.previous')}
-        onClick={() => {
-          if (page.month - 1 < 0) {
-            setPage({ month: 11, year: page.year - 1 })
-          } else {
-            setPage({ ...page, month: page.month - 1 })
-          }
-        }}
+        onClick={() => setPage(page.subtract({ months: 1 }))}
         icon={<ChevronLeft />}
       />
-      <span>{dayjs.months()[page.month]} {page.year}</span>
+      <span>{page.toPlainDate({ day: 1 }).toLocaleString(i18n.language, { month: 'long', year: 'numeric' })}</span>
       <Button
         title={t<string>('form.dates.tooltips.next')}
-        onClick={() => {
-          if (page.month + 1 > 11) {
-            setPage({ month: 0, year: page.year + 1 })
-          } else {
-            setPage({ ...page, month: page.month + 1 })
-          }
-        }}
+        onClick={() => setPage(page.add({ months: 1 }))}
         icon={<ChevronRight />}
       />
     </div>
 
     <div className={styles.dayLabels}>
-      {(rotateArray(dayjs.weekdaysShort(), -weekStart)).map(name =>
+      {(rotateArray(getWeekdayNames(i18n.language, 'short'), weekStart)).map(name =>
         <label key={name}>{name}</label>
       )}
     </div>
@@ -96,27 +73,27 @@ const Month = ({ value, onChange }: MonthProps) => {
           className={makeClass(
             styles.date,
             date.month !== page.month && styles.otherMonth,
-            date.isToday && styles.today,
+            date.equals(Temporal.Now.plainDateISO()) && styles.today,
             (
-              (!(mode.current === 'remove' && selecting.includes(date.str)) && value.includes(date.str))
-              || (mode.current === 'add' && selecting.includes(date.str))
+              (!(mode.current === 'remove' && selecting.includes(date.toString())) && value.includes(date.toString()))
+              || (mode.current === 'add' && selecting.includes(date.toString()))
             ) && styles.selected,
           )}
-          key={date.str}
-          title={`${date.day} ${dayjs.months()[date.month]}${date.isToday ? ` (${t('form.dates.tooltips.today')})` : ''}`}
+          key={date.toString()}
+          title={`${date.toLocaleString(i18n.language, { day: 'numeric', month: 'long' })}${date.equals(Temporal.Now.plainDateISO()) ? ` (${t('form.dates.tooltips.today')})` : ''}`}
           onKeyDown={e => {
             if (e.key === ' ' || e.key === 'Enter') {
-              if (value.includes(date.str)) {
-                onChange(value.filter(d => d !== date.str))
+              if (value.includes(date.toString())) {
+                onChange(value.filter(d => d !== date.toString()))
               } else {
-                onChange([...value, date.str])
+                onChange([...value, date.toString()])
               }
             }
           }}
           onPointerDown={e => {
             startPos.current = { x, y }
-            mode.current = value.includes(date.str) ? 'remove' : 'add'
-            setSelecting([date.str])
+            mode.current = value.includes(date.toString()) ? 'remove' : 'add'
+            setSelecting([date.toString()])
             e.currentTarget.releasePointerCapture(e.pointerId)
 
             document.addEventListener('pointerup', handleFinishSelection, { once: true })
@@ -129,10 +106,10 @@ const Month = ({ value, onChange }: MonthProps) => {
                   found.push({ y: cy, x: cx })
                 }
               }
-              setSelecting(found.map(d => dates[d.y][d.x].str))
+              setSelecting(found.map(d => dates[d.y][d.x].toString()))
             }
           }}
-        >{date.day}</button>)
+        >{date.toLocaleString(i18n.language, { day: 'numeric' })}</button>)
       )}
     </div>
   </>
@@ -140,32 +117,19 @@ const Month = ({ value, onChange }: MonthProps) => {
 
 export default Month
 
-interface Date {
-  str: string
-  day: number
-  month: number
-  isToday: boolean
-}
-
 /** Calculate the dates to show for the month in a 2d array */
-const calculateMonth = (date: Dayjs, weekStart: 0 | 1) => {
-  const daysInMonth = date.daysInMonth()
-  const daysBefore = date.date(1).day() - weekStart
-  const daysAfter = 6 - date.date(daysInMonth).day() + weekStart
+const calculateMonth = (month: Temporal.PlainYearMonth, weekStart: 0 | 1) => {
+  const daysBefore = month.toPlainDate({ day: 1 }).dayOfWeek - (weekStart ? 0 : 1)
+  const daysAfter = 6 - month.toPlainDate({ day: month.daysInMonth }).dayOfWeek + (weekStart ? 0 : 1)
 
-  const dates: Date[][] = []
-  let curDate = date.date(1).subtract(daysBefore, 'day')
+  const dates: Temporal.PlainDate[][] = []
+  let curDate = month.toPlainDate({ day: 1 }).subtract({ days: daysBefore })
   let y = 0
   let x = 0
-  for (let i = 0; i < daysBefore + daysInMonth + daysAfter; i++) {
+  for (let i = 0; i < daysBefore + month.daysInMonth + daysAfter; i++) {
     if (x === 0) dates[y] = []
-    dates[y][x] = {
-      str: curDate.format('DDMMYYYY'),
-      day: curDate.date(),
-      month: curDate.month(),
-      isToday: curDate.isToday(),
-    }
-    curDate = curDate.add(1, 'day')
+    dates[y][x] = curDate
+    curDate = curDate.add({ days: 1 })
     x++
     if (x > 6) {
       x = 0
diff --git a/frontend/src/components/CalendarField/components/Weekdays/Weekdays.tsx b/frontend/src/components/CalendarField/components/Weekdays/Weekdays.tsx
index 9d922ae..f77d375 100644
--- a/frontend/src/components/CalendarField/components/Weekdays/Weekdays.tsx
+++ b/frontend/src/components/CalendarField/components/Weekdays/Weekdays.tsx
@@ -1,7 +1,7 @@
 import { useCallback, useMemo, useRef, useState } from 'react'
-import { rotateArray } from '@giraugh/tools'
+import { range, rotateArray } from '@giraugh/tools'
+import { Temporal } from '@js-temporal/polyfill'
 
-import { useDayjs } from '/src/config/dayjs'
 import { useTranslation } from '/src/i18n/client'
 import { useStore } from '/src/stores'
 import useSettingsStore from '/src/stores/settingsStore'
@@ -11,22 +11,17 @@ import { makeClass } from '/src/utils'
 import styles from '../Month/Month.module.scss'
 
 interface WeekdaysProps {
-  /** Array of weekdays as numbers from 0-6 (as strings) */
+  /** dayOfWeek 1-7 as a string */
   value: string[]
   onChange: (value: string[]) => void
 }
 
 const Weekdays = ({ value, onChange }: WeekdaysProps) => {
-  const { t } = useTranslation('home')
-  const dayjs = useDayjs()
+  const { t, i18n } = useTranslation('home')
 
-  const weekStart = useStore(useSettingsStore, state => state.weekStart) ?? 0
+  const weekStart = useStore(useSettingsStore, state => state.weekStart) ?? 1
 
-  const weekdays = useMemo(() => rotateArray(dayjs.weekdaysShort().map((name, i) => ({
-    name,
-    isToday: dayjs().day() === i,
-    str: String(i),
-  })), -weekStart), [weekStart])
+  const weekdays = useMemo(() => rotateArray(range(1, 7).map(i => Temporal.Now.plainDateISO().add({ days: i - Temporal.Now.plainDateISO().dayOfWeek })), weekStart), [weekStart])
 
   // Ref and state required to rerender but also access static version in callbacks
   const selectingRef = useRef<string[]>([])
@@ -54,27 +49,27 @@ const Weekdays = ({ value, onChange }: WeekdaysProps) => {
         type="button"
         className={makeClass(
           styles.date,
-          day.isToday && styles.today,
+          day.equals(Temporal.Now.plainDateISO()) && styles.today,
           (
-            (!(mode.current === 'remove' && selecting.includes(day.str)) && value.includes(day.str))
-            || (mode.current === 'add' && selecting.includes(day.str))
+            (!(mode.current === 'remove' && selecting.includes(day.dayOfWeek.toString())) && value.includes(day.dayOfWeek.toString()))
+            || (mode.current === 'add' && selecting.includes(day.dayOfWeek.toString()))
           ) && styles.selected,
         )}
-        key={day.name}
-        title={day.isToday ? t<string>('form.dates.tooltips.today') : undefined}
+        key={day.toString()}
+        title={day.equals(Temporal.Now.plainDateISO()) ? t<string>('form.dates.tooltips.today') : undefined}
         onKeyDown={e => {
           if (e.key === ' ' || e.key === 'Enter') {
-            if (value.includes(day.str)) {
-              onChange(value.filter(d => d !== day.str))
+            if (value.includes(day.dayOfWeek.toString())) {
+              onChange(value.filter(d => d !== day.dayOfWeek.toString()))
             } else {
-              onChange([...value, day.str])
+              onChange([...value, day.dayOfWeek.toString()])
             }
           }
         }}
         onPointerDown={e => {
           startPos.current = i
-          mode.current = value.includes(day.str) ? 'remove' : 'add'
-          setSelecting([day.str])
+          mode.current = value.includes(day.dayOfWeek.toString()) ? 'remove' : 'add'
+          setSelecting([day.dayOfWeek.toString()])
           e.currentTarget.releasePointerCapture(e.pointerId)
 
           document.addEventListener('pointerup', handleFinishSelection, { once: true })
@@ -83,12 +78,12 @@ const Weekdays = ({ value, onChange }: WeekdaysProps) => {
           if (mode.current) {
             const found = []
             for (let ci = Math.min(startPos.current, i); ci < Math.max(startPos.current, i) + 1; ci++) {
-              found.push(weekdays[ci].str)
+              found.push(weekdays[ci].dayOfWeek.toString())
             }
             setSelecting(found)
           }
         }}
-      >{day.name}</button>
+      >{day.toLocaleString(i18n.language, { weekday: 'short' })}</button>
     )}
   </div>
 }
diff --git a/frontend/src/components/CreateForm/CreateForm.tsx b/frontend/src/components/CreateForm/CreateForm.tsx
index 4c6ffe3..755a7b3 100644
--- a/frontend/src/components/CreateForm/CreateForm.tsx
+++ b/frontend/src/components/CreateForm/CreateForm.tsx
@@ -3,6 +3,7 @@
 import { useState } from 'react'
 import { SubmitHandler, useForm } from 'react-hook-form'
 import { useRouter } from 'next/navigation'
+import { Temporal } from '@js-temporal/polyfill'
 
 import Button from '/src/components/Button/Button'
 import CalendarField from '/src/components/CalendarField/CalendarField'
@@ -11,7 +12,6 @@ import SelectField from '/src/components/SelectField/SelectField'
 import TextField from '/src/components/TextField/TextField'
 import TimeRangeField from '/src/components/TimeRangeField/TimeRangeField'
 import { API_BASE } from '/src/config/api'
-import { useDayjs } from '/src/config/dayjs'
 import { useTranslation } from '/src/i18n/client'
 import timezones from '/src/res/timezones.json'
 
@@ -36,7 +36,6 @@ const defaultValues: Fields = {
 
 const CreateForm = () => {
   const { t } = useTranslation('home')
-  const dayjs = useDayjs()
   const { push } = useRouter()
 
   const {
@@ -58,38 +57,38 @@ const CreateForm = () => {
       if (dates.length === 0) {
         return setError(t('form.errors.no_dates'))
       }
-      const isSpecificDates = dates[0].length === 8
       if (time.start === time.end) {
         return setError(t('form.errors.same_times'))
       }
 
-      const times = dates.reduce((times, date) => {
+      // If format is `YYYY-MM-DD` or `d`
+      const isSpecificDates = dates[0].length !== 1
+
+      const times = dates.reduce((times, dateStr) => {
         const day = []
+        const date = isSpecificDates
+          ? Temporal.PlainDate.from(dateStr)
+          : Temporal.Now.plainDateISO().add({ days: Number(dateStr) - Temporal.Now.plainDateISO().dayOfWeek })
+
         for (let i = time.start; i < (time.start > time.end ? 24 : time.end); i++) {
+          const dateTime = date.toZonedDateTime({ timeZone: timezone, plainTime: Temporal.PlainTime.from({ hour: i }) }).withTimeZone('UTC')
           if (isSpecificDates) {
-            day.push(
-              dayjs.tz(date, 'DDMMYYYY', timezone)
-                .hour(i).minute(0).utc().format('HHmm-DDMMYYYY')
-            )
+            // Format as `HHmm-DDMMYYYY`
+            day.push(`${dateTime.hour.toString().padStart(2, '0')}${dateTime.minute.toString().padStart(2, '0')}-${dateTime.day.toString().padStart(2, '0')}${dateTime.month.toString().padStart(2, '0')}${dateTime.year.toString().padStart(4, '0')}`)
           } else {
-            day.push(
-              dayjs().tz(timezone)
-                .day(Number(date)).hour(i).minute(0).utc().format('HHmm-d')
-            )
+            // Format as `HHmm-d`
+            day.push(`${dateTime.hour.toString().padStart(2, '0')}${dateTime.minute.toString().padStart(2, '0')}-${String(dateTime.dayOfWeek === 7 ? 0 : dateTime.dayOfWeek)}`)
           }
         }
         if (time.start > time.end) {
           for (let i = 0; i < time.end; i++) {
+            const dateTime = date.toZonedDateTime({ timeZone: timezone, plainTime: Temporal.PlainTime.from({ hour: i }) }).withTimeZone('UTC')
             if (isSpecificDates) {
-              day.push(
-                dayjs.tz(date, 'DDMMYYYY', timezone)
-                  .hour(i).minute(0).utc().format('HHmm-DDMMYYYY')
-              )
+              // Format as `HHmm-DDMMYYYY`
+              day.push(`${dateTime.hour.toString().padStart(2, '0')}${dateTime.minute.toString().padStart(2, '0')}-${dateTime.day.toString().padStart(2, '0')}${dateTime.month.toString().padStart(2, '0')}${dateTime.year.toString().padStart(4, '0')}`)
             } else {
-              day.push(
-                dayjs().tz(timezone)
-                  .day(Number(date)).hour(i).minute(0).utc().format('HHmm-d')
-              )
+              // Format as `HHmm-d`
+              day.push(`${dateTime.hour.toString().padStart(2, '0')}${dateTime.minute.toString().padStart(2, '0')}-${String(dateTime.dayOfWeek === 7 ? 0 : dateTime.dayOfWeek)}`)
             }
           }
         }
diff --git a/frontend/src/components/Recents/Recents.tsx b/frontend/src/components/Recents/Recents.tsx
index 51397ed..f831ae7 100644
--- a/frontend/src/components/Recents/Recents.tsx
+++ b/frontend/src/components/Recents/Recents.tsx
@@ -1,13 +1,14 @@
 'use client'
 
 import Link from 'next/link'
+import { Temporal } from '@js-temporal/polyfill'
 
 import Content from '/src/components/Content/Content'
 import Section from '/src/components/Section/Section'
-import { useDayjs } from '/src/config/dayjs'
 import { useTranslation } from '/src/i18n/client'
 import { useStore } from '/src/stores'
 import useRecentsStore from '/src/stores/recentsStore'
+import { relativeTimeFormat } from '/src/utils'
 
 import styles from './Recents.module.scss'
 
@@ -17,8 +18,7 @@ interface RecentsProps {
 
 const Recents = ({ target }: RecentsProps) => {
   const recents = useStore(useRecentsStore, state => state.recents)
-  const { t } = useTranslation(['home', 'common'])
-  const dayjs = useDayjs()
+  const { t, i18n } = useTranslation(['home', 'common'])
 
   return recents?.length ? <Section id="recents">
     <Content>
@@ -28,8 +28,8 @@ const Recents = ({ target }: RecentsProps) => {
           <span className={styles.name}>{event.name}</span>
           <span
             className={styles.date}
-            title={dayjs.unix(event.created_at).format('D MMMM, YYYY')}
-          >{t('common:created', { date: dayjs.unix(event.created_at).fromNow() })}</span>
+            title={Temporal.Instant.fromEpochSeconds(event.created_at).toLocaleString(i18n.language, { dateStyle: 'long' })}
+          >{t('common:created', { date: relativeTimeFormat(Temporal.Instant.fromEpochSeconds(event.created_at), i18n.language) })}</span>
         </Link>
       ))}
     </Content>
diff --git a/frontend/src/components/Settings/Settings.tsx b/frontend/src/components/Settings/Settings.tsx
index 260025e..1f85dcc 100644
--- a/frontend/src/components/Settings/Settings.tsx
+++ b/frontend/src/components/Settings/Settings.tsx
@@ -3,6 +3,7 @@
 import { useCallback, useEffect, useRef, useState } from 'react'
 import { useRouter } from 'next/navigation'
 import { maps } from 'hue-map'
+import { MapKey } from 'hue-map/dist/maps'
 import { Settings as SettingsIcon } from 'lucide-react'
 
 import SelectField from '/src/components/SelectField/SelectField'
@@ -64,8 +65,8 @@ const Settings = () => {
               'Sunday': t('options.weekStart.options.Sunday'),
               'Monday': t('options.weekStart.options.Monday'),
             }}
-            value={store?.weekStart === 0 ? 'Sunday' : 'Monday'}
-            onChange={value => store?.setWeekStart(value === 'Sunday' ? 0 : 1)}
+            value={store?.weekStart === 1 ? 'Sunday' : 'Monday'}
+            onChange={value => store?.setWeekStart(value === 'Sunday' ? 1 : 0)}
           />
 
           <ToggleField
@@ -103,7 +104,7 @@ const Settings = () => {
             }}
             isSmall
             value={store?.colormap}
-            onChange={event => store?.setColormap(event.target.value)}
+            onChange={event => store?.setColormap(event.target.value as MapKey)}
           />
 
           <ToggleField
diff --git a/frontend/src/components/TimeRangeField/TimeRangeField.tsx b/frontend/src/components/TimeRangeField/TimeRangeField.tsx
index 4f05fcf..e82b22e 100644
--- a/frontend/src/components/TimeRangeField/TimeRangeField.tsx
+++ b/frontend/src/components/TimeRangeField/TimeRangeField.tsx
@@ -2,9 +2,10 @@
 
 import { useRef } from 'react'
 import { FieldValues, useController, UseControllerProps } from 'react-hook-form'
-import dayjs from 'dayjs'
+import { Temporal } from '@js-temporal/polyfill'
 
 import { Description, Label, Wrapper } from '/src/components/Field/Field'
+import { useTranslation } from '/src/i18n/client'
 import { useStore } from '/src/stores'
 import useSettingsStore from '/src/stores/settingsStore'
 
@@ -81,6 +82,7 @@ interface HandleProps {
 
 const Handle = ({ value, onChange, labelPadding }: HandleProps) => {
   const timeFormat = useStore(useSettingsStore, state => state.timeFormat)
+  const { i18n } = useTranslation()
 
   const isMoving = useRef(false)
   const rangeRect = useRef({ left: 0, width: 0 })
@@ -106,7 +108,7 @@ const Handle = ({ value, onChange, labelPadding }: HandleProps) => {
       left: `calc(${value * 4.166}% - 11px)`,
       '--extra-padding': labelPadding,
     } as React.CSSProperties}
-    data-label={timeFormat === '24h' ? times[value] : dayjs().hour(Number(times[value])).format('ha')}
+    data-label={Temporal.PlainTime.from({ hour: Number(times[value] === '24' ? '00' : times[value]) }).toLocaleString(i18n.language, { hour: 'numeric', hour12: timeFormat === '12h' })}
     onMouseDown={() => {
       document.addEventListener('mousemove', handleMouseMove)
       isMoving.current = true
diff --git a/frontend/src/config/dayjs.ts b/frontend/src/config/dayjs.ts
deleted file mode 100644
index 4e2729f..0000000
--- a/frontend/src/config/dayjs.ts
+++ /dev/null
@@ -1,47 +0,0 @@
-import { useCallback, useState } from 'react'
-import { isKeyOfObject } from '@giraugh/tools'
-import dayjs from 'dayjs'
-import customParseFormat from 'dayjs/plugin/customParseFormat'
-import isToday from 'dayjs/plugin/isToday'
-import localeData from 'dayjs/plugin/localeData'
-import relativeTime from 'dayjs/plugin/relativeTime'
-import timezone from 'dayjs/plugin/timezone'
-import updateLocale from 'dayjs/plugin/updateLocale'
-import utc from 'dayjs/plugin/utc'
-
-import { useTranslation } from '/src/i18n/client'
-import { languageDetails } from '/src/i18n/options'
-import { useStore } from '/src/stores'
-import useSettingsStore from '/src/stores/settingsStore'
-
-dayjs.extend(customParseFormat)
-dayjs.extend(isToday)
-dayjs.extend(localeData)
-dayjs.extend(relativeTime)
-dayjs.extend(timezone)
-dayjs.extend(updateLocale)
-dayjs.extend(utc)
-
-export const useDayjs = () => {
-  const { i18n } = useTranslation()
-  const store = useStore(useSettingsStore, state => state)
-  const [updateInstance, setUpdateInstance] = useState(0)
-
-  const instance = useCallback(dayjs, [updateInstance, dayjs])
-
-  const handleLanguageChange = useCallback((lng: string) => {
-    if (isKeyOfObject(lng, languageDetails)) {
-      store?.setWeekStart(languageDetails[lng].weekStart)
-      store?.setTimeFormat(languageDetails[lng].timeFormat)
-
-      languageDetails[lng]?.import().then(() => {
-        dayjs.locale(lng)
-        setUpdateInstance(updateInstance + 1)
-      })
-    }
-  }, [store])
-
-  i18n.on('languageChanged', handleLanguageChange)
-
-  return instance
-}
diff --git a/frontend/src/i18n/client.ts b/frontend/src/i18n/client.ts
index f8cad7b..9f876ae 100644
--- a/frontend/src/i18n/client.ts
+++ b/frontend/src/i18n/client.ts
@@ -2,12 +2,11 @@
 
 import { initReactI18next, useTranslation as useTranslationHook } from 'react-i18next'
 import { cookies } from 'next/dist/client/components/headers' // risky disky (undocumented???)
-import dayjs from 'dayjs'
 import i18next from 'i18next'
 import LanguageDetector from 'i18next-browser-languagedetector'
 import resourcesToBackend from 'i18next-resources-to-backend'
 
-import { cookieName, getOptions, languageDetails } from './options'
+import { cookieName, getOptions } from './options'
 
 i18next
   .use(initReactI18next)
@@ -24,11 +23,5 @@ i18next
       excludeCacheFor: [],
     },
   })
-  .then(() => {
-    // Set dayjs locale
-    languageDetails[i18next.resolvedLanguage as keyof typeof languageDetails]?.import().then(() => {
-      dayjs.locale(i18next.resolvedLanguage)
-    })
-  })
 
 export const useTranslation: typeof useTranslationHook = (ns, options) => useTranslationHook(ns, options)
diff --git a/frontend/src/i18n/options.ts b/frontend/src/i18n/options.ts
index 0c34047..b66dabf 100644
--- a/frontend/src/i18n/options.ts
+++ b/frontend/src/i18n/options.ts
@@ -27,89 +27,71 @@ interface LanguageDetails {
   /** 0: Sunday, 1: Monday */
   weekStart: 0 | 1
   timeFormat: '12h' | '24h'
-  /** The separator to show between hours and minutes (default `:`) */
-  separator?: string
-  /** Day.js locale import */
-  import: () => Promise<unknown>
 }
 
 export const languageDetails: Record<typeof languages[number], LanguageDetails> = {
   'en': { // English (US)
     name: 'English (US)',
-    import: () => import('dayjs/locale/en'),
     weekStart: 0,
     timeFormat: '12h',
   },
   'en-GB': { // English (UK)
     name: 'English (UK)',
-    import: () => import('dayjs/locale/en-gb'),
     weekStart: 1,
     timeFormat: '12h',
   },
   'de': { // German
     name: 'Deutsch',
-    import: () => import('dayjs/locale/de'),
     weekStart: 1,
     timeFormat: '24h',
   },
   'es': { // Spanish
     name: 'Español',
-    import: () => import('dayjs/locale/es'),
     weekStart: 1,
     timeFormat: '24h',
   },
   'fr': { // French
     name: 'Français',
-    import: () => import('dayjs/locale/fr'),
     weekStart: 1,
     timeFormat: '24h',
   },
   'hi': { // Hindi
     name: 'हिंदी',
-    import: () => import('dayjs/locale/hi'),
     weekStart: 1,
     timeFormat: '12h',
   },
   'id': { // Indonesian
     name: 'Indonesia',
-    import: () => import('dayjs/locale/id'),
     weekStart: 1,
     timeFormat: '24h',
-    separator: '.',
   },
   'ja': { // Japanese
     name: '日本語',
-    import: () => import('dayjs/locale/ja'),
     weekStart: 0,
     timeFormat: '12h',
   },
   'ko': { // Korean
     name: '한국어',
-    import: () => import('dayjs/locale/ko'),
     weekStart: 0,
     timeFormat: '24h',
   },
   'pl': { // Polish
     name: 'Polskie',
-    import: () => import('dayjs/locale/pl'),
     weekStart: 1,
     timeFormat: '12h',
   },
   'pt-BR': { // Portuguese (Brazil)
     name: 'Português (do Brasil)',
-    import: () => import('dayjs/locale/pt-br'),
     weekStart: 0,
     timeFormat: '24h',
   },
   'ru': { // Russian
     name: 'Pусский',
-    import: () => import('dayjs/locale/ru'),
     weekStart: 1,
     timeFormat: '24h',
   },
   // 'zh-CN': { // Chinese
   //   name: '中文',
-  //   import: () => import('dayjs/locale/zh-cn'),
   //   weekStart: 1,
   //   timeFormat: '12h',
   // },
diff --git a/frontend/src/i18n/server.ts b/frontend/src/i18n/server.ts
index 5704fce..abecf38 100644
--- a/frontend/src/i18n/server.ts
+++ b/frontend/src/i18n/server.ts
@@ -1,10 +1,9 @@
 import { cookies, headers } from 'next/headers'
 import acceptLanguage from 'accept-language'
-import dayjs from 'dayjs'
 import { createInstance } from 'i18next'
 import resourcesToBackend from 'i18next-resources-to-backend'
 
-import { cookieName, fallbackLng, getOptions, languageDetails, languages } from './options'
+import { cookieName, fallbackLng, getOptions, languages } from './options'
 
 type Mutable<T> = { -readonly [K in keyof T]: Mutable<T[K]> }
 
@@ -25,11 +24,6 @@ export const useTranslation = async (ns: string | string[], options: { keyPrefix
     ?? acceptLanguage.get(headers().get('Accept-Language'))
     ?? fallbackLng
 
-  // Set dayjs locale
-  languageDetails[language as keyof typeof languageDetails]?.import().then(() => {
-    dayjs.locale(language)
-  })
-
   const i18nextInstance = await initI18next(language, ns)
   return {
     t: i18nextInstance.getFixedT(language, Array.isArray(ns) ? ns[0] : ns, options.keyPrefix),
diff --git a/frontend/src/stores/settingsStore.ts b/frontend/src/stores/settingsStore.ts
index bc1ab61..1332499 100644
--- a/frontend/src/stores/settingsStore.ts
+++ b/frontend/src/stores/settingsStore.ts
@@ -1,4 +1,4 @@
-import { ColorMap } from 'hue-map/dist/maps'
+import { MapKey } from 'hue-map/dist/maps'
 import { create } from 'zustand'
 import { persist } from 'zustand/middleware'
 
@@ -6,17 +6,18 @@ type TimeFormat = '12h' | '24h'
 type Theme = 'System' | 'Light' | 'Dark'
 
 interface SettingsStore {
+  /** 0: Monday, 1: Sunday */
   weekStart: 0 | 1
   timeFormat: TimeFormat
   theme: Theme
   highlight: boolean
-  colormap: 'crabfit' | ColorMap
+  colormap: 'crabfit' | MapKey
 
   setWeekStart: (weekStart: 0 | 1) => void
   setTimeFormat: (timeFormat: TimeFormat) => void
   setTheme: (theme: Theme) => void
   setHighlight: (highlight: boolean) => void
-  setColormap: (colormap: 'crabfit' | ColorMap) => void
+  setColormap: (colormap: 'crabfit' | MapKey) => void
 }
 
 const useSettingsStore = create<SettingsStore>()(persist(
@@ -33,7 +34,18 @@ const useSettingsStore = create<SettingsStore>()(persist(
     setHighlight: highlight => set({ highlight }),
     setColormap: colormap => set({ colormap }),
   }),
-  { name: 'crabfit-settings' },
+  {
+    name: 'crabfit-settings',
+    version: 1,
+    migrate: (persistedState, version) => {
+      if (version === 0) {
+        // Weekstart used to be 0 for Sunday, but now it's been swapped
+        (persistedState as SettingsStore).weekStart = (persistedState as SettingsStore).weekStart === 1 ? 0 : 1
+        return persistedState as SettingsStore
+      }
+      return persistedState as SettingsStore
+    },
+  },
 ))
 
 export default useSettingsStore
diff --git a/frontend/src/utils/convertTimesToDates.ts b/frontend/src/utils/convertTimesToDates.ts
index ec48dfa..0cfb448 100644
--- a/frontend/src/utils/convertTimesToDates.ts
+++ b/frontend/src/utils/convertTimesToDates.ts
@@ -1,7 +1,7 @@
 import { Temporal } from '@js-temporal/polyfill'
 
 /**
- * Take times as strings and convert to Dayjs objects
+ * Take times as strings in UTC and convert to ZonedDateTime objects in the timezone supplied
  * @param times An array of strings in `HHmm-d` or `HHmm-DDMMYYYY` format
  * @param timezone The target timezone
  */
diff --git a/frontend/yarn.lock b/frontend/yarn.lock
index 6cec2ec..11ccfa0 100644
--- a/frontend/yarn.lock
+++ b/frontend/yarn.lock
@@ -645,11 +645,6 @@ damerau-levenshtein@^1.0.8:
   resolved "https://registry.yarnpkg.com/damerau-levenshtein/-/damerau-levenshtein-1.0.8.tgz#b43d286ccbd36bc5b2f7ed41caf2d0aba1f8a6e7"
   integrity sha512-sdQSFB7+llfUcQHUQO3+B8ERRj0Oa4w9POWMI/puGtuf7gFywGmkaLCElnudfTiKZV+NvHqL0ifzdrI8Ro7ESA==
 
-dayjs@^1.11.7:
-  version "1.11.7"
-  resolved "https://registry.yarnpkg.com/dayjs/-/dayjs-1.11.7.tgz#4b296922642f70999544d1144a2c25730fce63e2"
-  integrity sha512-+Yw9U6YO5TQohxLcIkrXBeY73WP3ejHWVvx8XCk3gxvQDCTEmS48ZrSZCKciI7Bhl/uCMyxYtE9UqRILmFphkQ==
-
 debug@^3.2.6, debug@^3.2.7:
   version "3.2.7"
   resolved "https://registry.yarnpkg.com/debug/-/debug-3.2.7.tgz#72580b7e9145fb39b6676f9c5e5fb100b934179a"