The ability to set your own custom time frames in the Water Overlay. This makes it possible to set a time frame (T=0) at the beginning of your scenario as a initial situation. This new feature also gives you the option to make better comparisons with your measurement data, because you can set specific dates and times. Another positive effect of this new feature is that, in contrast to the standard functionality, you no longer have to divide the time frames linearly. This makes it possible to have your own relevant timestamps over a longer periode of time for rainfall calculations.
More info:
https://previewsupport.tygron.com/wiki/Version_2021.5.1
https://previewsupport.tygron.com/wiki/Timestamp
https://previewsupport.tygron.com/wiki/How_to_set_custom_timeframes
https://previewsupport.tygron.com/wiki/Timeframes_(Water_Overlay)