This will be super short two step guide.
All you need to do is:
1. Go to the object you want to perform this action,
2. Click on the "New" button to create a new field
3. Select Formula type field
4. Name the field and select the field format
5. And than all you need to do is use this DATETIMEVALUE formula to achieve the result.
I hope this was useful and helped somebody with the struggle.
Have a great day. ;)