include \masm32\MasmBasic\MasmBasic.inc ; download
Init
MovVal ST(0), Input$("\nConsumption: ", "500") ; ask e.g. for cubic metres of water
movaps xmm1, TimeSF(Input$("older date: ", fDate$(-30))) ; suggest thirty days before today
psubq TimeSF(Input$("newer date: ", fDate$())), xmm1 ; subtract from today
FpuPush TimeDiff(d)
Print Str$("%i days between the two dates\n", ST(0)) ; display difference in days
fdiv
Inkey Str$("Consumption per day: %3f units", ST(0)v) ; calculate consumption per day
EndOfCodeThe strings "500",
fDate$(-30) and
fDate$() are suggestions and can be edited by the user with the arrow and backspace keys. The consumption can be any number, e.g. 1.5; the dates must be entered in the correct format dd.mm.yyyy - sorry, U.S. format won't work

Example:
Consumption: 500
older date: 29.01.2022
newer date: 29.05.2022
120 days between the two dates
Consumption per day: 4.17 units
Macros used: MovVal, Input$(), TimeSF(), fDate$(), TimeDiff(), FpuPush, Str$(), Inkey