Filter on last user modified (#8093)

Example: `userdate:PT1H` to select only articles modified by user during the last hour
Fix https://github.com/FreshRSS/FreshRSS/issues/4280#issuecomment-3393078024

Useful for instance to bulk mark as unread recently marked articles by error:
1. Click on the toggle button to show the read articles (making sure the toggle for the unread articles is off)
2. Sort by *User modified 9→1*
3. Filter by *user modified date*, for instance to the last 3 hours by typing `userdate:PT3H`
4. Click in the drop-down menu *Mark selection as unread*

P.S.: I have added at the same time a bunch of unit tests for date-related logic

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/lib_date.php b/lib/lib_date.php
index 9d4bcaa07..a44710da1 100644
--- a/lib/lib_date.php
+++ b/lib/lib_date.php
@@ -74,7 +74,7 @@ function _dateRelative(?string $d1, ?string $d2): ?string {
 	if ($d2 === null) {
 		return $d1 !== null && $d1[0] !== 'P' ? $d1 : null;
 	}
-	if ($d2 !== '' && $d2[0] != 'P' && $d1 !== null && $d1[0] !== 'P') {
+	if ($d2 !== '' && $d2[0] !== 'P' && $d1 !== null && $d1[0] !== 'P') {
 		$y2 = substr($d2, 0, 4);
 		if (strlen($y2) < 4 || !ctype_digit($y2)) {	//Does not start by a year
 			$d2 = _noDelimit($d2);
@@ -91,7 +91,7 @@ function _dateRelative(?string $d1, ?string $d2): ?string {
  */
 function parseDateInterval(string $dateInterval): array {
 	$dateInterval = trim($dateInterval);
-	$dateInterval = str_replace('--', '/', $dateInterval);
+	$dateInterval = str_replace(['--', ' '], ['/', 'T'], $dateInterval);
 	$dateInterval = strtoupper($dateInterval);
 	$min = null;
 	$max = null;