GMT-7 is a time offset that subtracts 7 hours from Greenwich Mean Time (GMT). This means that the local time is 7 hours behind GMT. It is observed in certain regions such as the Mountain Standard Time (MST) zone during standard time, and in the Pacific Daylight Time (PDT) zone during daylight saving time months. Some locations also use this offset year-round. In practice, GMT-7 means when it is noon in GMT (Greenwich, London), the time in GMT-7 zones would be 5:00 AM. This time zone is used in parts of North America including areas like Arizona, parts of Canada, and the western United States during specific times of the year. Notably, GMT-7 is different from GMT+7, which is 7 hours ahead of GMT and used in parts of Southeast Asia. Summary:

• GMT-7 = GMT minus 7 hours (7 hours behind GMT)
• Used in Mountain Standard Time (MST), Pacific Daylight Time (PDT), and some locations year-round
• Common in parts of North America
• GMT-7 does not observe Daylight Saving Time in all regions, but some switch to PDT which corresponds to GMT-7 during daylight saving months

This offset allows synchronization of time across different geographic locations by adjusting hours relative to GMT. If you meant GMT+7 instead, that is a zone 7 hours ahead of GMT commonly used in Southeast Asia. Let me know if you want details on a specific location or how this relates to other time zones.