"That timezone is 5 hours ahead of ours" clearly means a difference of +5 hours (relative to us), but I came across a different wording of it: "that timezone is 5 hours earlier than ours". If I'm not mistaken, both of these statements do mean the same thing, right?
To me, however, the first statement makes much more sense and is less ambiguous.
Best Answer
As the earth rotates from west to east, if location B is to the east of location A, then location B will experience sunrise, noon, sunset, etc, earlier than location A, but, if the separation is considerable, location B will be in a different time zone, so that its clocks show a later time than those in location A. If the time is 12 noon here in the UK, it is 5 pm in India, which is five hours ahead (later), but it is 7 am in Florida, USA, which is five hours behind (earlier). You can resolve any perceived ambiguity by making it clear whether you are considering the earth's rotation, or the relative clock times of the different zones. Since time zones are intended to provide suitable local clock times, many people will interpret an 'earlier time zone' as one where the clocks show an earlier time.
The New York Times, commenting in 1983 on the consolidation of Alaska's four time zones into two, said that "More than 98 percent of the state's population is in ... Yukon time, which is one hour earlier than Pacific standard time and four hours earlier than Eastern standard time." Yukon time was renamed 'Alaska time' later that year. Alaska Time is UTC minus 9 hours; Pacific standard time is UTC minus 8 hours. When it is 9 AM PST, it is 8 AM Alaska time, one hour earlier. Thus, the Alaska time zone is discussed as being the 'earlier' zone.
My Commonwealth cousins in New Zealand will let off their New Year fireworks when my phone says it is 11 AM on December 31.
Time Zone Map