This is one of those things that has been too hard for years. If 2022 is going to be the year that the UX gets tighter, it would be wonderful to have built-in sensors to provide many common date functions to make automations very easy to set up in the UI. Thanks for considering this.
Obviously, there are many other date and time values but it’s impractical to make sensors of all of them by default and triggering by time and/or date is already handled by the Time Trigger.
However, if for some reason you need it as a sensor, you could simply make a Template Sensor. There’s also the Time & Date integration which creates a few date and time sensors (personally I don’t use it because now() provides the same and more).