The problem I often see with Census data is that Census takers (& those interviewed) rounded up and rounded down ages… even when they weren’t fibbing.
Some prople figured age as of January 1 or December 31… or actually precisely considered the day of the census and their birthday. So Census can only reliably calculate a birth year range.
Calculated implies a level of accuracy that can’t be achieved with Census within the constraints of GEDCOM. And, for better or worse, the GEDCOM specification has influenced design specs for most genealogy software.
The decrepit GEDCOM standard only supports 1 DATE_APPROXIMATED modifier: About, Calculated, Estimated. Or you can also use a DATE_RANGE: Before, After, Between. But it doesn’t permit combining the attributes as an approximated (calculated) range (between).
(If your range fell within a calendar month or year, you COULD imply a range by dropping the day or month. That is fully compatible with the Calculated spec.)
Gramps currently does support combining dates ranges with approximations! And another current thread here is discussing eliminating that for the GEDCOM export because it fails compliance testing.
See
It’s a conundrum.