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The view period can be changed by selecting the button "Period history time slider" (button with the clock and arrows).
The t0 can be set to the selected time in the time slider by the button button "Set t0 to the selected time".
If a location is not visible at the selected time in the time slider, the location will still be shown in the map and the filter, but will be greyed out to indicate thatit that it is not valid at the selected time.
For performance reasons the icons in the filters will not be updated according to the selected time when the time slider is shown in the map display. Activating the time slider
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