Your display has:
Mar 20, 2014 @ 17:58 20/03/2014 16:58 UTC
Jun 21, 2012 @ 07:46 21/06/2012 05:46 UTC
Sep 22, 2012 @ 23:19 22/09/2012 21:19 UTC
Dec 21, 2012 @ 18:47 21/12/2012 17:47 UTC
On my WD 10.37R-(b81) system I get
03/20/2014 9:58am 20 March 2014 16:58 UTC
06/21/2014 3:52am 21 June 2014 10:52 UTC
09/22/2014 7:30pm 23 September 2014 02:30 UTC
12/21/2014 3:04pm 21 December 2014 23:04 UTC
Using the built-in template calculations (such as for WeatherLink template) I get
03/20/2014 9:57am 20 March 2014 16:57 GMT
06/21/2014 3:51am 21 June 2014 10:51 GMT
09/22/2014 7:29pm 23 September 2014 02:29 GMT
12/21/2014 3:03pm 21 December 2014 23:03 GMT
and those values are from the US Naval Observatory.
Looks like your maybe some other script is interfering with
the values in $marchequinox, $junesolstice, $sepequinox, $decsolstice from Weather-Display.
Your testtags.php?sce=view shows
$marchequinox = '16:58 UTC 20 marzo 2014'; // March equinox date
$junesolstice = '10:52 UTC 21 giugno 2014'; // June solstice date
$sepequinox = '02:30 UTC 23 settembre 2014'; // September equinox date
$decsolstice = '23:04 UTC 21 dicembre 2014'; // December solstice date
Your Settings.php has $SITE['monthNames'] = array( // for wxastronomy page .. replace with month names in your language
'Gennaio','Febbraio','Marzo','Aprile','Maggio','Giugno',
'Luglio','Agosto','Settembre','Ottobre','Novembre','Dicembre'
);
so the dates should be handled correctly.
So.. WD looks clean. The issue is likely in some other part of the wxastronomy.php page where there is interference with the variable names... you're not running the 'stock' wxastronomy.php page .. you might try uploading the stock page as wxastronomy-orig.php and see if that has the same issue. If not, then it's some other scripting on your current page.
Best regards,
Ken