Understanding Time Zones When Traveling Internationally

March 10, 2015

The Rolling Stones sing, “Time is on my side, yes, it is” – and, since they’ve been around for what seems like 125 years, they just might be right about that!  But if reaching your vacation destination involves crossing the International Date Line and flying through several Time Zones, you might end up feeling that time is definitely not on your side!

If you do any international travel, you should take the ‘time’ to familiarize yourself with these very important terms: Time Zones, Greenwich Mean Time (GMT) / Prime Meridian, the International Date Line (IDL), and the 24-hour clock.  Following is an extremely simplified explanation of these terms:

Time Zones

Simply put, there are 24 Time Zones (based loosely on our 24 hour day) around the globe and each is separated by a one-hour time difference.  The earth is a sphere which is divided into 360 degrees by lines of longitude running north to south.  The earth rotates 360 degrees over a 24 hour period.  Dividing 360 degrees by 24 hours, it follows that the earth turns 15 degrees each hour; therefore, each time zone is 15 degrees wide.  In reality, of course, there is more to it than that.  Factor in Daylight Savings Time and Time Zones that extend beyond that 15 degrees to accommodate country borders or the need for uniformity and the words of the band Chicago may buzz in your head!  “Does anybody really know what time it is?  Does anybody really care?”.

Here’s an example of why you need to care! If it’s 9:30 PM on May 1 when you and your travel gear take off on XYZ Airlines from the west coast of the U.S. or Canada for a 12-15 hour flight to various destinations in Asia, such as Japan or Hong Kong, you might arrive there in the morning 2 calendar days later (May 3).  If you aren’t aware that you’ll be ‘missing’ one entire day (May 2), and you have scheduled a tour for May 2, you’ll be out of luck.

GMT/Prime Meridian (also known as UTC – Universal Time Coordinated)

One of those ‘lines of longitude’, mentioned above, passes through Greenwich, England and is known as the Prime Meridian.  The Time Zone at the Prime Meridian is zero (0 degrees) and each Time Zone around the globe is plus or minus the number of hours from Greenwich time, or Greenwich Mean Time (GMT).

International Date Line

The International Date Line (IDL) is an arbitrary line that runs down the opposite side of the globe from the Prime Meridian.  The date changes at the International Date Line (IDL) so that when it is noon in Greenwich, it is midnight at the International Date Line.  And, vice versa, when it is midnight in Greenwich at the Prime Meridian (0 degrees), it is noon at the International Date Line.  Or…in plain English….when it is Tuesday 2:00 PM in Honolulu, Hawaii; it is Wednesday 10:00 AM in Sydney, Australia as these cities are situated on either side of the IDL.

24-Hour Clock

The times of travel between or within foreign countries are generally displayed on airport arrival & departure boards, schedule displays, boarding passes, etc. using the 24-Hour Clock.  The 24-Hour Clock eliminates the AM/PM distinction and provides a different figure for each hour of the day.  Starting with 0000 (Midnight), a 24-hour day progresses from 0100 (1:00 AM) to 2300 (11:00 PM).  Minutes are indicated in a conventional way so that 0645 is 6:45 AM, 1845 is 6:45 PM and 2319 is 11:19 PM.

It’s easy enough to convert to the 24-Hour Clock by using the following tips:

  1. The first 12 hours of the day (AM) beginning one hour after midnight are hours 0100 through 1200. (You would say this as “o one hundred through twelve hundred.”)  To convert these AM hours to the 24-hour clock, drop the “AM” and add a 0 in front when necessary to arrive at a 4-digit figure:
    • 2:00 AM becomes 0200
    • 5:00 AM becomes 0500
  2. The second 12 hours of the day (PM) beginning immediately after 12 noon, are hours 1300 through 2359.  To convert these PM hours to the 24-hour clock, drop the “PM” and add 12 hours:
    • 2:00 PM becomes 1400  (2 + 12 = 14)
    • 5:00 PM becomes 1700  (5 + 12 = 17)

Tip:  If you wear a watch..er…’timepiece’, as soon as you are settled on the airplane, set it to the current time at your holiday destination.  This helps a little with ‘tricking’ your brain to adjust to the local time it will be when you arrive.  Your phone, computer, tablet, etc. should automatically switch to the local time at your destination.

By familiarizing yourself with these terms, examining your vacation timetable to ensure you know what day/date it will be when you arrive, and adjusting your destination plans accordingly…you and your luggage will be well on your way to a restful and enjoyable holiday!  And…isn’t it about ‘time’ for that??

 Written by Emma Ghattas