[sync] contact dates of birth are time-shifted by one day to the past when syncing from horde to mobile

[lists.horde.org at pqaudio.de]

Hi,

when horde sents a contact with active sync to my mobile phone, the date
of birth is shifted by one hour into the past.

As we only need the know the date for birthdays, we don't have extra
data like a timestamp stored within the database. But we have a varchar
field with a size of 10 to store iso formatted dates. But thats no
problem, PHP will threat those dates with a timestamp of 00:00:00. All
dates of birth in the database (table `horde_contacts`, fieldname
`object_bday`) are right. But a look into the ActiveSync Log file
offers, that somewhere must be done some date/time calculation magic
that a birthday eg. "1980-03-10" is exported as "1980-03-09T23:00:00.000Z"

But this only occurs, when a contact is synced from horde to my mobile
phone. The other direction works fine, also calendar entries are synced
as expected.

My php default date/time zone is set to 'Europe/Berlin'.

Online research and a lot of debug approaches did not help. Now i'm
unsure if its a horde problem or maybe some misconfiguration in my
installation.

Does anyone has the same or similar problem or knows about this?

Thank you in advance.

Patrick