# Clock

> Provides time-related operations for retrieving current time in various units, accessing date-time information, and non-blocking sleep functionality.

Clock service contains some functionality related to time and scheduling. 

To get the current time in a specific time unit, the `currentTime` function takes a unit as `TimeUnit` and returns `UIO[Long]`:

```scala compile-only

val inMilliseconds: UIO[Long] = Clock.currentTime(TimeUnit.MILLISECONDS)
val inDays        : UIO[Long] = Clock.currentTime(TimeUnit.DAYS)
```

To get current date time in the current timezone the `currentDateTime` function returns a ZIO effect containing `OffsetDateTime`.

Also, the Clock service has a very useful functionality for sleeping and creating a delay between jobs. The `sleep` takes a `Duration` and sleeps for the specified duration. It is analogous to `java.lang.Thread.sleep` function, but it doesn't block any underlying thread. It's completely non-blocking.

In the following example we are going to print the current time periodically by placing a one second `sleep` between each print call:

```scala compile-only

def printTimeForever: ZIO[Any, Throwable, Nothing] =
  Clock.currentDateTime.flatMap(Console.printLine(_)) *>
    ZIO.sleep(1.seconds) *> printTimeForever
```

For scheduling purposes like retry and repeats, ZIO has a great data type called [Schedule](../schedule/index.md).