From DipWiki

Defining Time in Diplomaticcorp Deadlines.

The Diplomaticcorp community is international. This means that in any one game, players will be from various locations around the world. These locations are likely to be in different time zones, with each time zone having its own different local time.

However, each game needs a standard time for deadlines. This deadline is set by the GM, based various factors – possibly the GM’s local time zone. Sometimes this time is expressed using the GM’s local time zone, sometimes using another. It may also be expressed using the international standard - UTC.

UTC (Universal Co-ordinated Time, Temps Universel Coordonné) is for all practical purposes the same as the old standard – GMT or Greenwich Mean Time (the time at the 0 degree prime meridian at Greenwich, London when daylight saving is not in force). Both UTC and GMT are the same as the often used military and aviation time – ZULU or Z time.

If a GM uses the deadline facility on the game page then this is expressed in UTC.

The game page will show the current time expressed in UTC. This is calculated using the player’s own computer system clock, so if this clock is not set correctly then the correct UTC time will not be shown.

If a GM does not use the game page facility to express deadline times then check with the GM which time zone they are using and whether the deadline times will be constant or change due to daylight saving or other factors. It is the responsibility of the player to understand and make allowance for the differences between their own local time and the deadline’s time so that orders are not submitted late. Particular care should be taken when the player’s local time changes because of daylight saving.

Diplomacy games can take sometime to complete and often run over the points where local daylight saving time either starts or ends.

UTC is never subject to daylight saving time changes. This is the same if the GM is using GMT. In summer, Greenwich itself is -1 hour GMT or +0 hours BST (British Summer Time). If your local area is subject to daylight saving you will find that the difference between your local time and UTC will change at the start and end of the daylight saving period. This period starts and ends on different dates, in different locations, around the world, and also for the Northern and Southern Hemispheres. Local times to the west of the prime meridian are usually behind UTC; those to the east are usually in advance of UTC. Those bordering the Prime Meridian can be the same, or just behind UTC. Not all areas within the same time zone use daylight saving, or the same amount of daylight saving time, or daylight saving time over the same period of the year.