Time and daylight saving

Location tab on model data at Site level

Time zone

Select the Time zone for the site location. The time zone defines both the standard time meridian and information on daylight saving. Generally you should leave this as the default for the location.

You can override daylight savings to be off by unchecking the Use daylight saving model data.

DesignBuilder models the effect of daylight saving time where the clocks are moved forward one hour in the summer months in most non-equatorial countries. The timing of this is handled automatically using the Time zones database when you load data from one of the Location templates supplied with the program.

There are some factors you should be aware of:

In EnergyPlus, summer Daylight saving works by adding the number of hours specified in the Time zone data (usually 1 hour) to the local mean time to get the time to determine schedule operation. Because Simulation results are displayed in local mean time, during the summer when daylight saving time is in use, occupancy and equipment etc will appear to start 1 hour earlier in the day than it does in the winter. To help you pinpoint this, DesignBuilder prints the times when daylight saving starts and ends on the graph.
When comparing results with and without Daylight saving you will notice:

Solar radiation data has exactly the same timing with and without daylight saving.
Occupancy, equipment (and other aspects of building operation controlled by schedules) will start 1 hour earlier with daylight saving.

Visualisations use local mean time when setting the position of the sun for site shading analysis. Again you can account for daylight saving time by adding 1 hour to the time during summer months to see shading for local clock time.

Start/End of Winter/Summer

These settings are loaded from the Location template and cannot be edited in Model data.

For Northern hemisphere locations you should normally expect to see data like:

Start of Winter = Oct
End of Winter = Mar
Start of Summer = Apr
End of Summer = Sep

For Southern hemisphere locations you should normally expect to see data like:

Start of Winter = Apr
End of Winter = Sep
Start of Summer = Oct
End of Summer = Mar

Note: It is important that the selected months cover the entire year.