For example, when a country changes time, there are 2 possibilities:
1.- If it changes to an earlier time, for example, at 3 Am in Central Europe, the last Sunday in October at 3 Am becomes 2 Am, therefore, if there is a date that is 02:30 am, 2 Dates and Hours are possible, one before the Change, and one after the Change.
2.- In Central Europe the Last Sunday of March at 2 Am becomes 3 Am, therefore if someone puts a date/time like this: 03-31-2024 at 02:30 Am, that LOCAL time It is theoretically impossible, since between 2 and 3 there is no possibility of Local Time.
Is there any code that warns about this?
For example, I have this code in PHP, I pass it a time zone, and it does not warn me that this time, 02:30:00Am, is not officially possible, and I would like it to warn me about these conflicting hours:
(The code has an error in JulianDay, below I make a comment with the correction, it is a small error, the link is already corrected)
https://timezonespro.com/php/test4.php?tzname=Europe/Madrid
<?php
$timezoneStr = $_GET["tzname"];
echo "TimeZone = " . $timezoneStr;
$datetime = "2024-03-31 02:30:00";
print '<br>';
echo "Local = " . $datetime;
$given = new DateTime($datetime, new DateTimeZone($timezoneStr));
$given->setTimezone(new DateTimeZone("UTC"));
$output = $given->format("Y-m-d H:i:s");
print '<br>';
echo "UTC = " . $output;
$ano = substr($output, 0, 4);
$mes = substr($output, 5, 2);
$dia = substr($output, 8, 2);
$hor = substr($output, 11, 2);
$min = substr($output, 14, 2);
$sec = substr($output, 17, 2);
print '<br>';
echo "Year = " . $ano;
print '<br>';
echo "Month = " . $mes;
print '<br>';
echo "Day = " . $dia;
print '<br>';
echo "Hours = " . $hor;
print '<br>';
echo "Minutes = " . $min;
print '<br>';
echo "Seconds = " . $sec;
$meses = ["Enero", "Febrero", "Marzo", "Abril", "Mayo", "Junio", "Julio", "Agosto", "Septiembre", "Octubre", "Noviembre", "Diciembre"];
$mesStr = $meses[intval($mes) - 1];
print '<br>';
echo $dia . "-" . $mesStr . "-" . $ano . " a las " . $hor . ":" . $min . ":" . $sec;
$secondsInTime = intval($hor * 3600) + intval($min * 60) + intval($sec);
$secondsInTimeDec = $secondsInTime / 86400;
$jd = GregorianToJD($mes, $dia, $ano);
$jdDec = intval($jd) + $secondsInTimeDec;
print '<br>';
echo "JulianDay = " . $jdDec;
?>
A code that warns of conflicting times in time changes in a country.
DateTime already handles such cases:
$dt = new DateTime('2024-03-31 02:30:00', new DateTimeZone('Europe/Madrid'));
echo $dt->format('Y-m-d H:i:s'); // prints: 2024-03-31 03:30:00
Notice how the "impossible" 02:30 became 03:30 automatically.
There is no warning, but you can always compare the formatted Y-m-d H:i:s strings of the date with and without timezone info, if you need to check if that happened.