Android/Kotlin Date DSL

DateExtension.kt

inline fun date(timeInMillis: Long = System.currentTimeMillis(), block: SimpleDate.() -> Unit = {}): SimpleDate {
    val dateDsl = SimpleDate()
    dateDsl.timeInMillis = timeInMillis
    block(dateDsl)
    return dateDsl
}


class SimpleDate {

    private val calendar: Calendar = Calendar.getInstance()

    var timeInMillis = System.currentTimeMillis()
        get() = calendar.timeInMillis
        set(value) {
            calendar.timeInMillis = value
            field = value
        }

    var date = Date()
        get() = calendar.time
        set(value) {
            calendar.time = value
            field = value
        }
    
    fun format(pattern: String, locale: Locale = Locale.US): String {
        return SimpleDateFormat(pattern, locale).format(date)
    }
    
    val nextDay: SimpleDate get() = addDay(1)
    val nextWeek: SimpleDate get() = addDay(7)
    val nextYear: SimpleDate get() = addYear(1)
    val nextNextMonth: SimpleDate get() = addMonth(1)
    
    fun addDay(day: Int): SimpleDate {
        this.day += day
        return this
    }

    fun addYear(year: Int): SimpleDate {
        this.year += year
        return this
    }

    fun addMonth(month: Int): SimpleDate {
        this.month += month
        return this
    }

    fun addHour(hour: Int): SimpleDate {
        this.hour += hour
        return this
    }

    fun addMinute(minute: Int): SimpleDate {
        this.minute += minute
        return this
    }

    fun addSecond(second: Int): SimpleDate {
        this.second += second
        return this
    }

    fun addMillisecond(millisecond: Int): SimpleDate {
        this.millisecond += millisecond
        return this
    }

    var year = calendar.get(Calendar.YEAR)
        set(value) {
            calendar.set(Calendar.YEAR, value); field = value
        }
    var day = calendar.get(Calendar.DAY_OF_MONTH)
        set(value) {
            calendar.set(Calendar.DAY_OF_MONTH, value); field = value
        }
    var dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK)
        set(value) {
            calendar.set(Calendar.DAY_OF_WEEK, value); field = value
        }
    var month = calendar.get(Calendar.MONTH) + 1
        set(value) {
            calendar.set(Calendar.MONTH, value - 1); field = value
        }
    var hour = calendar.get(Calendar.HOUR)
        set(value) {
            calendar.set(Calendar.HOUR, value); field = value
        }
    var minute = calendar.get(Calendar.MINUTE)
        set(value) {
            calendar.set(Calendar.MINUTE, value); field = value
        }
    var second = calendar.get(Calendar.SECOND)
        set(value) {
            calendar.set(Calendar.SECOND, value); field = value
        }
    var millisecond = calendar.get(Calendar.MILLISECOND)
        set(value) {
            calendar.set(Calendar.MILLISECOND, value); field = value
        }
}

Main.kt

fun main() {
  
 val now = date()
 val nowAsDate : Date = now.date
 val nowYear = now.year // 2018
 val nowMonth = now.month // 11
 val nowInMillis = now.timeInMillis

 val hoursAheadFromNow = date().addHour(1)
 val tomorrow = date().nextDay
 val nextWeek = date().nextWeek
 val nextYear = date().nextYear
  
 val formattedTomorrow = tomorrow.format("yyyy MM dd hh:mm:ss")
 
 val nextYearAprilFools = date {
   month = 4; day = 1
   hour = 0; minute = 0; second = 0; millisecond = 0
 }.nextYear
  
 val initTimeInMillis = date(timeInMillis = System.currentTimeMillis())
 
}