Try the Natural Language Dates plugin. It adds a command to pick a date from a calendar and will transform what you write after an “@” into a properly formatted date.
You can also use the “Insert Current Date” and “Insert Current Time” commands from the Natural Language Dates plugin, assigning these to whatever hotkeys you like. Also, if you go into the preferences for that plugin, you can choose the desired date/time format. I use this to quickly insert the current time-of-day using command-shift-T. It works brilliantly.
Depending on your platform, you could use a third party app to bind keystrokes to expand to the desired results. For example, on macOS, I’ve set ;sdt as a keystroke to expand as STAMP DATE TIME (YYYY-MM-DD HH:MM) using Keyboard Maestro.
I’m using Alfred snippet for this kind of “smart” and frequently used content.
I also create some templates for the text whose content is almost static and is used only a few times a day or a week.