CalendarUtils.kt

 fun setTimeToStartOfDay(calendar: Calendar): Calendar {
        calendar.set(Calendar.HOUR_OF_DAY, 0)
        calendar.set(Calendar.MINUTE, 0)
        calendar.set(Calendar.SECOND, 0)
        calendar.set(Calendar.MILLISECOND, 0)
        return calendar
}

fun setTimeToEndOfDay(calendar: Calendar): Calendar {
    calendar.set(Calendar.HOUR_OF_DAY, 23)
    calendar.set(Calendar.MINUTE, 59)
    calendar.set(Calendar.SECOND, 59)
    calendar.set(Calendar.MILLISECOND, 999)
    return calendar
}

fun setTimeTo(calendar: Calendar, hourOfDay: Int, minute: Int): Calendar {
    calendar.set(Calendar.HOUR_OF_DAY, hourOfDay)
    calendar.set(Calendar.MINUTE, minute)
    calendar.set(Calendar.SECOND, 0)
    calendar.set(Calendar.MILLISECOND, 0)
    return calendar
}

fun setDateTo(calendar: Calendar, year: Int, month: Int, dayOfMonth: Int): Calendar {
    calendar.set(Calendar.YEAR, year)
    calendar.set(Calendar.MONTH, month - 1)
    calendar.set(Calendar.DAY_OF_MONTH, dayOfMonth)
    return calendar
}

fun zeroSecondsAndMs(calendar: Calendar): Calendar {
    calendar.set(Calendar.SECOND, 0)
    calendar.set(Calendar.MILLISECOND, 0)
    return calendar
}

fun addMinutes(calendar: Calendar, minute: Int) {
    calendar.add(Calendar.MINUTE, minute)
}

fun subtractMinutes(calendar: Calendar, minute: Int) {
    calendar.add(Calendar.MINUTE, -minute)
}

fun isSameDay(c1: Calendar, c2: Calendar): Boolean {
    return c1.get(Calendar.YEAR) == c2.get(Calendar.YEAR) && c1.get(Calendar.DAY_OF_YEAR) == c2.get(Calendar.DAY_OF_YEAR)
}

fun addDays(calendar: Calendar, days: Int) {
    calendar.add(Calendar.DAY_OF_MONTH, days)
}

fun subtractDays(calendar: Calendar, days: Int) {
    calendar.add(Calendar.DAY_OF_MONTH, -days)
}

fun newCalendarInstance(time: Long): Calendar {
    val cal = Calendar.getInstance()
    cal.timeInMillis = time
    return cal
}

fun newCalendarInstance(date: Date): Calendar {
    val cal = Calendar.getInstance()
    cal.timeInMillis = date.time
    return cal
}

fun newCalendarInstance(year: Int, month: Int, dayOfMonth: Int): Calendar {
    val cal = Calendar.getInstance()
    setTimeToStartOfDay(cal)
    return setDateTo(cal, year, month, dayOfMonth)
}

fun newCalendarInstance(hourOfDay: Int, minute: Int): Calendar {
    val cal = Calendar.getInstance()
    return setTimeTo(cal, hourOfDay, minute)
}