GMT times do not change, but remember that the market opens/closes at the LOCAL market times. Daylight savings moves the GMT time relative to the local time because banks in that locality will open at a certain time, all year long.
For example, New York banks open at 8 am local time. If daylight savings pushes the time back an hour, New York banks don't open at 7am to match GMT time, they still open at 8 am local time. See how it changes? The opening time in terms of GMT would shift an hour, not the local time.
We hope this helps. If you have any further questions, comments or suggestions, please do not hesitate to contact us at any time. Thanks, good luck and good trading!