I also want to share my own thoughts on this topic.
Regarding “estimated” and “calculated,” I see the benefit of using both options.
When I choose “calculated,” it lets other researchers know that I have derived this date based on other documents, which I am now adding to the citations. Although I didn’t always add these citations before, seeing “calculated” informs the researcher that a calculation has been made, which can be personally verified by doing the same. This is particularly relevant for “confession lists,” where the age of village residents is known and an approximate birth year can be calculated.
When I choose “estimated,” this might be an approximate date based on what my relatives have told me. It is not calculated, but I am aware of it. I also use “estimated” when making assumptions such as: if a child was born on 1800-01-01, it means the parents likely got married before this date. In this case, I add “estimated” to explain that it is my personal assessment and not a 100% historical fact.
Regarding “about,” “after,” “before.”
First, can we allow setting the value “0” in the “Calculation limits” settings? For new users, date/age calculations based on these “Calculation limits” raise more questions than they provide answers. I think these three settings:
Date ‘about’ year range: (date ± #)
Date ‘after’ year range: (date ± #)
Date ‘before’ year range: (date ± #)
should be set to “0” by default. At the same time, I like Davesellers’ proposal:
Nevertheless, I would allow setting values to “0.” This way, I would disable these settings at least until they start considering different levels of accuracy for different dates like 1800, 1800-02, 1800-02-15.