src/timetable: Break out leap_years_since function from doomsday

diff --git a/src/timetable.lua b/src/timetable.lua
index c71c59bc25d737ebc27c60b0586b719dd1d25c8f..b58ad0f531cc8386904e5aca72a8d21445126e44 100644 (file)
--- a/src/timetable.lua
+++ b/src/timetable.lua
@@ -27,9 +27,13 @@ local function month_length ( m , y )
        end
 end
 
+local function leap_years_since ( year )
+       return idiv ( year , 4 ) - idiv ( year , 100 ) + idiv ( year , 400 )
+end
+
 local function doomsday ( year )
        return ( 3 -- Tuesday
-               - 1 + year + idiv ( year , 4 ) - idiv ( year , 100 ) + idiv ( year , 400 ) )
+               - 1 + year + leap_years_since ( year ) )
                % 7 + 1
 end
 local doomsday_cache = setmetatable ( { } , {