Textarea field with a variable word inside?

[notflip]

I have a textarea field, in which my client can add text, inside this text there will be an amount of days (until the event), for example

We're counting down! {{ amountOfDays }} until the event happens!

This will be calculated using the current date, minus a global set date, is this possible using Statamic?

[ryanmitchell]

Yes, you select the following field in the config:

Then you can specify the days as a variable in your template or in a view model

[notflip]

Thanks @ryanmitchell I managed to output that variable! I'm wondering though, the output is from another date field, I want to compute the amount of days between then and now, I looked at the computed properties documentation but it seems that's only for Users and Collections, do I need to use JS to read, process and overwrite the data in that div? Or can statamic tell me the difference in days between two dates?