You have a large dataset that contains more than 1 million rows. The table has a datetime column named Date.

You need to reduce the size of the data model.

What should you do?

A. Round the hour of the Date column to startOfHour.
B. Change the data type of the Date column to Text.
C. Trim the Date column.

D. Split the Date column into two columns, one that contains only the time and another that contains only the date.

Explanation: We have to separate date & time tables. Also, we don’t need to put the time into the date table, because the time is repeated every day.
Split your DateTime column into a separate date & time columns in fact table, so that you can join the date to the date table & the time to the time table. The time need to be converted to the nearest round minute or second so that every time in your data corresponds to a row in your time table.

Reference:
https://intellipaat.com/community/6461/how-to-include-time-in-date-hierarchy-in-power-bi