Hovering over dates in various places in Pastel will show you the full date and time (ie. canvases on the dashboard, comments, and replies).
Each canvas will have a default date shown on when the canvas was created. When you hover over that date, you will be shown a tooltip with the exact date and time.
If you ever need to see the date and time a comment was left in a canvas, you can do so by looking at the comment in the canvas's sidebar.
Each comment will have a default date shown on how long ago the comment/reply was left. When you hover over that, you will be shown a tooltip with the exact date and time.