shiftDayTimeToTimezone.spec.ts

import moment from 'moment-timezone'

export const shiftUtcDayTimeToTimezone = (
  utcDayTime: string,
  timezone: string
) => {
  const offsetMinutes = moment.tz(moment.utc(), timezone).utcOffset()
  const [hours, minutes] = utcDayTime.split(':')
  const quotient = Math.floor(offsetMinutes / 60)
  const remainder = offsetMinutes % 60

  return `${Number(hours) + quotient}:${Number(minutes) + remainder}`
}



describe('shiftDayTimeToTimezone', () => {
  it('should shift', async () => {
    expect(
      shiftUtcDayTimeToTimezone('08:40', 'Europe/Prague')
    ).toMatchInlineSnapshot(`"10:40"`)

    expect(
      shiftUtcDayTimeToTimezone('8:40', 'Europe/Prague')
    ).toMatchInlineSnapshot(`"10:40"`)

    expect(
      shiftUtcDayTimeToTimezone('08:40', 'Europe/London')
    ).toMatchInlineSnapshot(`"9:40"`)

    expect(
      shiftUtcDayTimeToTimezone('08:40', 'America/New_York')
    ).toMatchInlineSnapshot(`"4:40"`)
  })
})