MITEL PBX time and date can be adjusted using the front desk console:

 MITEL SX50   

ADJUST TIME: Dail *15 HHMM in 24 hour format.
Example: 9:23 AM = *150923 then press release.
For PM hours you must add 12 hours to the HH setting.

ADJUST DATE: Dial *80 DD MM YY
Example: Feb 5th 2015 dial *80 05 02 15

MITEL SX200

ADJUST TIME: Press FUNCTION button, F2, Then look for Adjust time, enter the time in 24 hour clock HHMM then press release. You can also adjust the date on this same screen

These instructions are also listed in your MITEL manual that we provide.