That reads like two different requests.
If you want a time-based trigger, then you specify a shortcut top run at a particular time using Shortcuts’ personal automations (i*OS).
If you want to trigger a shortcut in a non-time-based way (NFC tag tap, manual run, geo-fence, etc.) and then decide what to do based on the time, you would do it exactly as you have described.
Here’s an example of one way you could do this.
Hope that helps.