I want to pre-populate a date based on current date calculation and selection of another field

Page 2 of survey:

Customer selection - Select Tier 1, Tier 1 requires 6 weeks to execute (30 business days).

Opt 1:

 If the customer then selects live date based on current date is less than 6 weeks (30 business days) can the system flag this as not enough days? 

Opt 2:

Can the form pre-populate to 6 weeks (30 business days)

Both options (1&2) are possible. But I suggest you used the Basic Date Picker field instead of the Date Picker widget for this as the widget does not work with Calculations.

Assign values to the "Select Tier" field.

You also need to add Short Text fields on the form to be used as placeholder for the calculated values.

then use Insert/Calculate conditions for the needed dates (number of days) calculations.

You can test my demo form https://www.jotform.com/202177672939971

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You can also clone my demo form using its URL https://www.jotform.com/202177672939971   so you can review in your Form Builder.

How to Clone an Existing Form from a URL

I hope this help. Let us know if you need further assistance.