instead of advance search of dates to be +/-, can it not be Boolean?
Short answer – probably possible, but definitely not easily. It is complicated due to our multi-cultural date feature (gregorian, julian, jewish, hijri, roman, french, jalali) both on input and output formatting. With some there can be over-laps at certain dates as well (e.g. the transition from gregorian to julian).
Where you see boolean dates available on search forms (other software) you are usually forced to be very precise about the format for date entry (e.g. mm/dd/yyyy = 01/12/1901 and NO exceptions). That really doesn’t work in our multi-lingual / multi-cultural environment too well.
What would be easy and might help slightly is to give you a wider range of +/- options. Perhaps add +/- 20 and +/- 50 yrs ? The latter would give you a full century.