# Calculator

GEDKeeper has an easy-to-use calculator, that allows you to evaluate expression using general mathematical operations and temporary variables.

This calculator can be useful when needing to process bulk information sources; for example, censuses or confessional books. You can work with the calculator and other windows side-by-side. Therefore, you can drag-and-drop a calculation result into a date field within the event editor dialog. Thus, while processing a source, you can enter the expression "1896-56" into the calculator (a year in a source "-" a persons' age "=" year of birth), press [`Enter`] to calculate, and then drag the result into a date field (the result is treated as a year).

If the "Copy result to clipboard" option is checked, the result is copied to the clipboard after the [`Enter`] key is pressed.

If you check the box "Events year calculation", then when the events dialog is open at the same time, the result will be automatically copied to the date field.