Question

Is there some function that can validate a date in format aaaa/mm/gg (ccyy/mm/dd) returning True if it is valid or False otherwise? I mean about really valid date, not only to level to syntax.

Answer 1

This is very fast, because the most simple errors are caught first.

function IsValidDate(const S: string): boolean;
var
  y, m, d: Integer;
const
  DAYS_OF_MONTH: array[1..12] of integer = (31, 29, 31, 30, 31, 30, 31, 31, 30,
  31, 30, 31);
begin
  result := false;
  if length(S) <> 10 then Exit;
  if (S[5] <> '/') or (S[8] <> '/') then Exit;
  if not TryStrToInt(Copy(S, 1, 4), y) then Exit;
  if not TryStrToInt(Copy(S, 6, 2), m) then Exit;
  if not InRange(m, 1, 12) then Exit;
  if not TryStrToInt(Copy(S, 9, 2), d) then Exit;
  if not InRange(d, 1, DAYS_OF_MONTH[m]) then Exit;
  if (not IsLeapYear(y)) and (m = 2) and (d = 29) then Exit;
  result := true;
end;