GMT is greenwich mean time.. and in greenwich the time is gtm +0 amsterdam is gmt +1 so 1 hour later than in greenwich
Greenwich GMT+0 14:00
Amsterdam GMT +1 15:00
Were orion lives GMT +5 19:00
Etc etc, you also have gmt -1.. -4.. etc etc than it would be like
Greenwich GMT+0 14:00
Blablaa GMT -3 11:00
Blablablaaa GMT -10 04:00
Get it?
My gmt is + 1 (amsterdam)
Select your country
here and scroll down to see your gmt / time in 24/12 hour time..