Is there a better way to capture age?

Our survey requires reporting, and skip logic, by age groups:

less than 28 days
less than 2 months
less than 5 years
less than 18 years
more than 5 years
more than 18 years

We cannot use birth date, since that is not always known, so this is really just an approximate age.

When I was using Enketo, I could lay out a grid for the age so that I could have a number field followed by a suffix (days, months, years). This worked great, but I cannot use the grid in KoBoCollect - which we have decided is our tool of choice.

I have come up with something that works, and I can do the necessary calculations, but the user interface is… less than ideal.

First the user chooses an age range

0 - 28 days
1 - 11 months
1 year or more

Then I have three Numeric questions, triggered by skip logic

Age - in DAYS
Age - in MONTHS
Age - in YEARS


If anyone has ideas for

  1. a better user interface or
  2. better data storage for calculations (maybe converting all ages to days, since I just need to report on age ranges? months x 30, years x 365??)
    please let me know.

Thanks as always.