When is 1st of February 24:00 (EST) time in GMT time in the UK? [closed]

ISO 8601 uses 24:00 specifically for midnight at the end of a day, and 00:00 for midnight at the start of a day. Thus, a flight that departs at 24:00 on Thursday, 1 February, U.S. Eastern Time is equivalent to one departing at 00:00 on Friday, 2 February, U.S. Eastern Time. Greenwich Mean Time would be 05:00 on Friday, 2 February.

U.S. Daylight Saving Time and British Summer Time begin and end on different dates, however, so check the offset if you are traveling during around the transitions.

In practice, I think carriers try to avoid the ambiguity and the customer service problems it will produce by scheduling a few minutes before or after, especially in the U.S. where the 12-hour clock is still predominant, even in travel settings.

For a magisterial treatment on the ambiguity see Why is 11 am + 1 hour == 12:00 pm? at English Language Learners.

EST is UTC-5, and 24:00 is usually a fairly uncommon but technically standard (ISO 8601) way of saying 00:00 the following day, so I would interpret this at 0500 February 2. However, it would be safest to check.

Note that once daylight savings time is in effect, some misuse EST when the region will really be on EDT (UTC-4), but this doesn't begin until March. Of course, once the UK goes on British Summer Time (BST) then they'll be UTC+1 as well.