#Until `eosio.cdt v1.6`

You could use:

 - `eosio::current_time()`
 - `now()`

#From eosio.cdt v1.6 onwards

You have to `#include <eosio/system.hpp>` and then you can use:

 - `eosio::current_time_point`
 - `eosio::current_block_time`