This would be a variable used for time enabled data/maps, such as maps using sliders. The variable would reference the current time being displayed in the map or on the slider.
This variable would allow new options for creating dynamic text/calculations in Arc Pro and AGOL, while also allowing dynamic symbology to be created. An example of application was given in the following forum post:
"For instance, if I wanted to create an arcade formula that changed symbology based on the difference between the date that the feature was created and the year currently being displayed in the time slider (say the feature was created in 2001, and each year that passed on the slider I wanted the transparency to increase or size to decrease...slider year - 2001 ....)? Or if I had a pop-up, and wanted the current date of the time slider to be shown."