One of the ways to express “when?” in Navajo is hádą́ą́’. You may recognize that -dą́ą́’ (ą́ą́’) particle which, like jį́į́dą́ą́’, refers to the past.
It effectively means “when in the past?”. This is separate from the way to say “when (in the future)?” in Navajo, which is hahgo.
Hádą́ą́’ Lucy Grand Canyongóó naayá? [When did Lucy go and get back from the Grand Canyon?]
In reply, you could use jį́į́dą́ą́, like in that post’s example. Or, to use “days ago” simply say the number of days, and then “yiskáńdą́ą́’”.
Díí’iskáńdą́ą́’ naayá. [Four days ago she went and came back.]