Do you know the difference? Don’t worry you are not alone. Many of the developers i have met or seen the code of , don’t know the difference either.
- GMT is Greenwich Mean Time whereas UTC is Coordinated Universal Time. Well this bit is obvious..
- GMT based on astronomical observations, used by countries associated with UK, UTC is based on atomic clocks and UTC is international standard recommended by the International Bureau of Weights and Measures (BIPM)
- Leap seconds are added to UTC to compensate for the slowing rotation of the Earth to track UT1 (which is the mean solar time at the Royal Observatory, Greenwich.)
- GMT is adopted by many countries i.e UK, ireland, Canada etc. UTC adapted by Internet and www standards, Network Time protocol (time sync) is based on UTC. GPS systems are based on UTC
- The actual time difference between the two is fractions of a second (0.9s to be precise) due to the fact that leap seconds are added.
- If fractions of a second are not important for you (it is important in many scientific measurements) then you can use GMT and UTC interchangeable since any timezone in the world would be in +ve or -ve offsets from the UTC
I hope this clarifies the difference a little?