The app does not use the device's time or time zone because users were found to be altering the date of their device, which resultantly changed the timestamp on the photo. This of course creates a significant issue regarding evidentiary integrity. Though you may not be using the app for evidence and only need a basic timestamp, the intended use of the app is for evidentiary purposes.
The app uses NTP (national time protocol), which uses the UTC international time standard. Due to the irregularity of the earth and the sun's movements, the exact time needs to be modified occasionally through the use of leap seconds. UTC provides this precise accuracy of time. UTC is based on zero degrees longitude and passes through the Greenwich Observatory so that atomic time is utilizes and leap seconds are added to the clock every so often. UTC was used beginning in the mid-twentieth century but became the official standard of world time on January 1, 1972.
UTC is 24-hour time, which begins at 0:00 at midnight. 12:00 is noon, 13:00 is 1 p.m., 14:00 is 2 p.m. and so on until 23:59, which is 11:59 p.m.
Because UTC time is indicated on the photo, users need to add/subtract their time zone differences to determine the image's local time. Users can find their time zone difference here: http://www.timeanddate.com/worldclock/converter.html
Obviously, it would not be fair to have the timestamp permanently maintain your specific time zone - others users in different time zones would not take kindly to this. UTC is the only time zone universally accepted around the World.
HOWEVER, due to customer demand, in a future update, users will be able to select whether or not they want to use their device time (i.e. local time) or UTC time.
I apologize if this has caused any inconvenience for you.