After the 1789 revolution in France, the revolutionaries not only dispensed with the ruling classes - they also created a new government, a new unit of measurement and (not so well known) a new metric calendar.

The calendar started in 1789 with this year becoming known as year one. Time was also divided into a new format: 100 seconds made a minute; 100 minutes an hour; 10 hours a day. A week lasted 10 days, and was known as a decade. Three of these decades made a month, and twelve 30-day months made a year. However, due to the fact that the earth, moon and sun did not fall into synch with the new regime, chaos ensued. The new calendar was five and a bit days short of the standard solar year and five extra days had to be added to the end. Decimal weeks now meant weekends fell every 10 days. Weekly markets and events became less frequent and hours almost doubled in length. It soon became extremely unpopular and on 31 December, 1805 Napoleon called time on the French Republican Calendar - a new year brought back the old regime.

Keeping in synch with GMT and European time - even without the added complication of different lengths of days and weeks - can be tricky enough. Thankfully it's easy to add, remove or change time zones with Outlook 2010. Whenever you need to keep track of what's going on at the other side of the world, you can change the time zone in Microsoft Outlook 2010 so that it matches any geographic location.

Changing the time zone is the same as changing the time zone in Control Panel in Windows. When you change the time zone setting in Outlook 2010, all Calendar views are updated so that they display the new time zone, and all Calendar items reflect the new time zone. And if you want your computer clock to automatically adjust for daylight saving time changes, all you need to do is select the Adjust for daylight saving time check box. Obviously this option is available only in time zones that use daylight saving time. And, obviously, the argument as to whether this is a sensible occurrence or not justifies an entirely new article.

When you adjust time zone and daylight saving time settings in Outlook, your Windows clock settings are also adjusted automatically. When Outlook is set to a time zone that observes daylight saving time, the clock adjusts for daylight saving time by default. When Outlook is set to a time zone that doesn't observe daylight saving time, such as Arizona in the United States, the daylight saving time adjustment obviously cannot be activated.

The start and end times for items in the Outlook Calendar are saved in the Co-ordinated Universal Time (UTC) format, an international time standard similar to Greenwich Mean Time. This means that when you send a meeting request to a colleague in Shanghai, for example, the meeting item is displayed at the local times on each person's calendar, but saved in UTC.

For example, a meeting organiser in the United Stated Pacific time zone sends a meeting request for 2pm. Pacific time to an attendee in the United States Mountain time zone. The attendee sees the meeting as starting at 3pm Mountain time. In both cases, the meeting is saved as starting at the same UTC time of 10:00pm. If two time zones are shown, the meeting organiser's time zone is used as the reference point. If you organise a meeting and display free/busy time for invitees from other time zones, their busy times are adjusted so that they appear correctly in your time zone. The second time zone is visible only when you view the calendar in day or week view.

Using the Outlook 2010 Time Zone tools is ideal if you need to add a second time zone to your Outlook view so that two separate time zones can be displayed in your Calendar. The two time zones can be, for example, your local time zone and the time zone of a city that you often have to travel to for meetings. The second time zone is used only to show a second time bar in Calendar view, and does not affect the way in which Calendar items are stored or displayed. When you have two time zones displayed in Calendar, you can swap their positions. So, as they say, when in Rome ...or Madrid... or even Paris now that the 10-day week is not likely to be part of any French Outlook calendar ... just do as they do.