Here are some common User Defined Actions you may come across a need for. I'm keeping this post short and sweet, as it's just to provde the User Defined Action files and they are fairly straight forward.
1. Get First Date of the Next Month
2. Get First Date of This Month
3. Get Last Date of This Month
4. Number of Days This Month
5. Number of Days Next Month
These were built based on a US format date (mm/dd/yyyy). So if you are located in a place like Australia, where the date format is (dd/mm/yyyy), you'll need to modify the Regular Expressions in the UDAs to cater for that.
To import these User Defined Actions, you will need to first go to create a new User Defined Action, and in the workflow designer, click on the Import button in the ribbon and import the file.