string_to_datetime and y2k problem [CORE6495]

[firebird-automations]

Submitted by: @ibprovider

string_to_datetime has following code for correction of y2k problem (two-digit year):

	tm times2;
	Firebird::TimeStamp::getCurrentTimeStamp\(\)\.decode\(&times2\);

	// Handle defaulting of year

	if \(description\[position\_year\] == 0\) \{
		times\.tm\_year = times2\.tm\_year \+ 1900;
	\}
	else if \(description\[position\_year\] <= 2\)
	\{
		// Handle conversion of 2\-digit years
		if \(times\.tm\_year < \(times2\.tm\_year \- 50\) % 100\)
			times\.tm\_year \+= 2000;
		else
			times\.tm\_year \+= 1900;
	\}

	times\.tm\_year \-= 1900;
	times\.tm\_mon \-= 1;

---
This code looks to the CURRENT year, but adjust the two-digit year number on 1900 or 2000.

When current year will be more than 2050, this code will return strange result.

[firebird-automations]

Commented by: @mrotteveel

Please define what you mean with "will return strange result", and why you think it is strange.

[firebird-automations]

Commented by: @asfernandes

This algorithm, if current year is 1990, is also strange.

It will make 80 be 2080, which would probably not be what one were thinking.

In the same way, we must decide how this will work when approaching 2100.