ParActual vs 30/360 day counts
Interest for part of a year depends on how you count the days. The two common conventions give different answers for the same dates.
Actual
Count the calendar days between the dates. US Treasury bonds and many loans use actual days, divided by 365 or by the actual days in the coupon period.
30/360
Treat every month as 30 days and the year as 360. Corporate and municipal bonds and many mortgages use it, because every month accrues the same interest. From March 14 to December 25 is 286 actual days but 281 days on a 30/360 basis.
Both at once
gΔDYSEEX gives the actual days in X and the 30/360 days in Y, so x≷y switches between them.