You’re not using it wrong. There is only 1 defined field of type “date”, and no possibility to create any other fields of the type “date”. See DATE - Custom Field Type - #165 by Melissa_Borup. There are partial workarounds.
There is no native calculated field (just column SUM, etc.). See calculated fields for projects - #8 by Adam_Finn There are 3rd party apps.
Compared to other software of all types I have used over the last 30-40 years, Asana requires 20x the workarounds and 3rd party apps to achieve essential functions.