# Timestamp Module
The Timestamp module provides functionality to get and set the on-chain time.
- [`timestamp::Trait`](https://docs.rs/pallet-timestamp/latest/pallet_timestamp/trait.Trait.html)
- [`Call`](https://docs.rs/pallet-timestamp/latest/pallet_timestamp/enum.Call.html)
- [`Module`](https://docs.rs/pallet-timestamp/latest/pallet_timestamp/struct.Module.html)
## Overview
The Timestamp module allows the validators to set and validate a timestamp with each block.
It uses inherents for timestamp data, which is provided by the block author and validated/verified
by other validators. The timestamp can be set only once per block and must be set each block.
There could be a constraint on how much time must pass before setting the new timestamp.
**NOTE:** The Timestamp module is the recommended way to query the on-chain time instead of using
an approach based on block numbers. The block number based time measurement can cause issues
because of cumulative calculation errors and hence should be avoided.
## Interface
### Dispatchable Functions
* `set` - Sets the current time.
### Public functions
* `get` - Gets the current time for the current block. If this function is called prior to
setting the timestamp, it will return the timestamp of the previous block.
### Config Getters
* `MinimumPeriod` - Gets the minimum (and advised) period between blocks for the chain.
## Usage
The following example shows how to use the Timestamp module in your custom module to query the current timestamp.
### Prerequisites
Import the Timestamp module into your custom module and derive the module configuration
trait from the timestamp trait.
### Get current timestamp
```rust
use frame_support::{decl_module, dispatch};
use frame_system::ensure_signed;
pub trait Config: timestamp::Config {}
decl_module! {
pub struct Module<T: Config> for enum Call where origin: T::Origin {
#[weight = 0]
pub fn get_time(origin) -> dispatch::DispatchResult {
let _sender = ensure_signed(origin)?;
let _now = <timestamp::Module<T>>::get();
Ok(())
}
}
}
```
### Example from the FRAME
The [Session module](https://github.com/paritytech/substrate/blob/master/frame/session/src/lib.rs) uses
the Timestamp module for session management.
## Related Modules
* [Session](https://docs.rs/pallet-session/latest/pallet_session/)
License: Apache-2.0