I try to use some formulas, but got error with parsing

1. date([field('MinimalStartDate').advance(years: 18), now()].max, now())

2. date([field('MinimalStartDate') + (18 * 365 + 4).days, now()].max, now())
3. date([field('MinimalStartDate') || Date.parse('2000-01-01').advance(years: 18), now()].max, now())
4. date([from_dataset('Players', 'birthDate', id: field('PlayerId')).advance(years: 18), now()].max, now())

but i got erros :
error: no implicit conversion of Time into String or error: Could not access blank value: Use || to provide a default value for blank fields. Example: (my_field || 0) + 1 or error: no implicit conversion of ActiveSupport::Duration into String