Warframe's servers run on Coordinated Universal Time (UTC) and the following counters are reset every day at 00:00 UTC:
- Login Counter
- Daily Trade/Gift Allowance
- Syndicate Reputation Caps
- Kubrow Interaction Cap
As all counters reset at 00:00 UTC, if for example you used up your last Trade at 23:59 UTC, in one minute at 00:00 UTC the next day, your trades will have returned to your maximum daily allowance.
Below is a handy time-zone converter to compare your time zone to Warframe's server time: https://www.worldtimebuddy.com/