Warframe's servers run on Coordinated Universal Time (UTC) and the following counters are reset every day at 00:00 GMT:
- Login Counter
- Daily Trade/Gift Allowance
- Syndicate Reputation Caps
- Kubrow Interaction Cap
As all counters reset at 00:00 GMT, if for example you used up your last Trade at 23:59 GMT, in one minute at 00:00 GMT 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:
http://www.greenwichmeantime.com/time-gadgets/time-zone-converter/index.htm