Title: Next or Prev working Day
Question: How to calculate the next/prev working day starting from a given date.
working days are monday to friday.
This article replaces the obsolete artice 2387
Answer:
type
// callback function for holidays
THolidayCallback = function(const d:TDateTime):boolean;
function PrevWorkingDay(const date:TDateTime; callback:THolidayCallback):TDateTime;
begin
Result := Int(date) - 1.0; // yesterday 0:00
if Assigned(callback) then
while (DayOfWeek(Result) in [1,7]) or callback(Result) do
Result := Result - 1.0
else
while (DayOfWeek(Result) in [1,7]) do
Result := Result - 1.0;
end;
function NextWorkingDay(const date:TDateTime; callback:THolidayCallback):TDateTime;
begin
Result := Int(date) + 1.0; // tomorrow 0:00
if Assigned(callback) then
while (DayOfWeek(Result) in [1,7]) or callback(Result) do
Result := Result + 1.0
else
while (DayOfWeek(Result) in [1,7]) do
Result := Result + 1.0;
end;
===========================================================================
// example for the callback function
function IsHoliday(const d:TDateTime):boolean;
var
year, month, day;
begin
DecodeDate(d, year, month, day);
if (month = 12) and ((day=25) or (day=26)) then
result := True // christmas
else if (month=12) and (day=31) then
result := True // sylvester
else if (month=1) (day=1) then
result := True;
// more queries here
// e.g. a lookup in a database
end;