A brief history of time zones
Theoretically, the world should be divided into 24 main time zones in which each zone differs from the last by one hour.
As time has gone on, things have changed. Time zones are irregular and affected by political, geographical and social changes.
BBC News website readers have been sharing their experiences of time and how it affects them when they interact and work with people across different time zones.
Libby and Edward Fisher, UK and Australia: Keep in touch with familyLibby Fisher, in the UK, regularly contacts her brother in Australia:
Having seen my brother only twice in the last three years, I've become adept at keeping in touch across two different time zones.
Currently, he is in Australia where the 11 hour time difference means it can be difficult to chat as he is winding down at the end of the day and I am just about ready to get the day started.
Weekends are generally perfect though, particularly if it is Sunday morning in the UK and Sunday evening in Australia as it gives enough time for a good catch-up.
By comparison, keeping in contact with my brother when he was in China was slightly easier with an eight hour time difference.
During the week, it is more difficult to keep in touch with someone in either Australia or China, as one person is trying to get out to work and the other is coming in from a long day, so keeping in touch via Facebook, email and text is much more convenient, although a bit impersonal.
The best way to keep in touch is to visit. I went to visit my brother in China and have a trip planned to Australia in the summer. Visiting friends and family across the world is really the best way to keep in touch.Edward Fisher speaks to his family in the UK from Australia:
Living in Australia but having family back in the UK is quite strange, because yes we are separated but at the same time we still maintain close links.
It became obvious early on that I was going to have limited contact with my family because of the different times zones.
My family and I solved this by emailing, and generally allowing a few days to respond. If it's more urgent, or just wanting to catch up, we do call each other, but either we call first thing in the morning or last thing at night.
We also try to pre-arrange our phone calls by email and plan a conversation schedule. It's no surprise that whoever is calling in the morning generally wants to spend the whole day talking, while the other frequently yawns on the other side!
If things are more urgent or if we just want to say a quick hi, then we send text messages.
Because of today's technology and good internet access being in a different time zone doesn't mean that my family are far away.
John Perry, Saudi Arabia: Keeps in touch with work
I am currently working in Riyadh where the working week is Saturday through Wednesday, with Thursday and Friday as the weekend.
I have been travelling to this area for thirty years and have never got used to the first day of the week being Saturday. It sounds very wrong to say "see you on Thursday", meaning "see you at the weekend."
Trying to communicate with someone back home can be a little difficult as there are only three working days that we have in common with the UK - Monday, Tuesday and Wednesday.
Coupled with this is the fact that we are currently +3 hours ahead of GMT. So 0900 on a Monday morning in the UK is midday Monday here. The only times when we can communicate effectively are 0900 to 1300 Monday, Tuesday and Wednesday, in other words, 12 hours per week.
This caused considerable problems for me recently when I needed access to legal advice. I was asked a question by my solicitors on Wednesday. I didn't see this email until Saturday when I replied directly. My solicitor didn't see my reply until midday my time Monday morning - thus an urgent matter was delayed by four days.
Transferring money via international banks can also have the same delay, meaning money can disappear for four days while it navigates two sets of weekends.
As we are working in a "global" market - people need to understand that we work in different time zones and have different working weeks.
Of course, when working for an American based company, things get far worse - I have been told to attend video conferences at 0300. It is one thing for a manager to expect their staff to be at work when they are, but when one's manager is in the US and you are in Saudi Arabia, things are a little different!
Tim Roach, Ontario, Canada: One place many times
When I worked in the High Arctic in the 1970s we were located geographically in the Mountain Time Zone but all of our communications were with Resolute Bay and Winnipeg so officially we were using Central Time.
However, our meteorological observations and twice daily balloon releases were co-ordinated on a world wide basis and set to Greenwich Mean Time.
In order to match mealtimes to the periods between balloon flights we set our living schedule to Atlantic Time.
All of this was only possible because we had 24 hours of daylight in summer.
Megan, UK: Playing online games across time zones
Role-playing games such as Dungeons and Dragons have entertained hordes of folks for years.
We play in groups and create an alternate reality devising and playing characters in a fantasy world. We describe what characters are doing and saying by rolling a strange-shaped dice.
We gather in each others homes and meet up at conventions to play, but with the growth of the internet other options have opened up.
Many games are now played by e-mail or in forums on discussion boards, but whilst these can be fun, nothing quite beats actually talking and interacting with other players in real-time which we can now do via the internet.
I'm currently running a game for two lovely people in America who are prepared to get up early in the morning so that we can play together.
It can take some complex scheduling to make sure everyone is around at the same time to play, and being in different time zones doesn't help, but when it all comes together it can be a blast!