Recurring events before year 1902 are not shown in calendar

Hi,

its hard to search for such specific issues in here so hope this wasn't reported before.

Setup:

DAVdroid 1.3.1 from F-Droid
Cyanogenmod 13 (latest nightly) with default calendar
ownCloud 9.0.5

Steps to reproduce:

Having a working ownCloud 9.0.5 installation
Create a contact with a birthday like 01.01.1900 (had chosen 1900 for contacts where i don't know their birthdays)
Configure DAVdroid to "All events will be synchronized"
Sync contacts and oC birthday calendar to Android device
Check Android Contact, the Birthday 01.01.1900 can be found there (As well as BDAY:1900-01-01 in the VCARD)
Check Android Calendar but the Birthday event won't show up
Check ownCloud Web-GUI and the Birthday event is showing up
Sync address book with SOGO Connector in Thunderbird and the Birthday event is showing up

After changing the birthday of the Contact from 01.01.1900 to 01.01.2000 the Birthday event is also showing up in the Android Calendar.

I'm not quite sure if this is an issue in DAVdroid or the Android Calendar itself. If any info is needed please let me know.

rfc2822

@Rancor In a first check, I couldn't reproduce that behavior with our Android 4.4 test device (Samsung Galaxy Note 10.1) and OwnCloud 9.1.1. The birthday BDAY:1900-10-04 becomes a VEVENT with

DTSTART;VALUE=DATE:19001004
DTEND;VALUE=DATE:19001005
RRULE:FREQ=YEARLY

which is correctly synchronized by DAVdroid and visible in the calendar app in Jan 2016. Can you maybe provide the VEVENT generated by OwnCloud? You can find it either using WebDAV or enable verbose logs on DAVdroid, change the birthday in OwnCloud and then synchronize with DAVdroid.

@rfc2822 Sorry for the delay and thanks for the reply. In the meantime i have updated to DAVdroid 1.3.2.2 to make sure that this is not already fixed.

Here are the VCARDS and VCALENDAR entries:

Birthday 13.10.1900

BEGIN:VCARD
VERSION:3.0
PRODID:-//Inverse inc.//SOGo Connector 1.0//EN
UID:C7423B0A-CCF0-0001-2FE1-4EF0A5A01A78.vcf
N:contact;test;;;
FN:test contact
X-MOZILLA-HTML:FALSE
BDAY:1900-10-13
END:VCARD

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Sabre//Sabre VObject 3.5.0//EN
CALSCALE:GREGORIAN
BEGIN:VEVENT
UID:C7423B0A-CCF0-0001-2FE1-4EF0A5A01A78.vcf
DTSTAMP:20161013T052841Z
DTSTART;VALUE=DATE:19001013
DTEND;VALUE=DATE:19001014
RRULE:FREQ=YEARLY
SUMMARY:test contact's Birthday (1900)
TRANSP:TRANSPARENT
END:VEVENT
END:VCALENDAR

Birthday 13.10.2000

BEGIN:VCARD
VERSION:3.0
PRODID:-//Inverse inc.//SOGo Connector 1.0//EN
UID:C7423B0A-CCF0-0001-2FE1-4EF0A5A01A78.vcf
N:contact;test;;;
FN:test contact
X-MOZILLA-HTML:FALSE
BDAY:2000-10-13
END:VCARD

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Sabre//Sabre VObject 3.5.0//EN
CALSCALE:GREGORIAN
BEGIN:VEVENT
UID:C7423B0A-CCF0-0001-2FE1-4EF0A5A01A78.vcf
DTSTAMP:20161013T053408Z
DTSTART;VALUE=DATE:20001013
DTEND;VALUE=DATE:20001014
RRULE:FREQ=YEARLY
SUMMARY:test contact's Birthday (2000)
TRANSP:TRANSPARENT
END:VEVENT
END:VCALENDAR

The 1900 Birthday won't show up in the Androids Calendar. After changing the year to 2000 and syncing again the Birthday Event will show up in Android.

I was also able to pinpoint the year where this is happening. An event of 13.10.1902 is shown in the calendar, anything below like 13.10.1901 won't show up.

Could it be that this is just a limitation on newer Androids (mine is CM13 / Android 6.0 where yours is Android 4.4)?

rfc2822

@Rancor I could reproduce the problem with CM13. It's funny

For instance, 1900-02-13 is UNIX time -2205273600 (2205273600 seconds before 1 Jan 1980 00:00 UTC). Because Android stores dtstart in milliseconds, it's -2205273600000. When the content provider is passed this value for the dtstart INTEGER SQLite field, it becomes 2089670400000 (Mar 21 2036 00:00 UTC), probaby because of the overflow of a int value in the provider: 32-bit signed int has a range from -2147483648 to +2147483647. If you scroll to Mar 2036, you will see this birthday (note that not only the year is incorrect, but the date is 21 Mar instead of 13 Feb because of the overflow).

However, if you use 1902-02-13, the dtstart inserted by DAVdroid is -2142201600000 [ms UNIX time]. This is now within the range of int and will be processed correctly.

Because DAVdroid provides the correct dtstart values to the Android calendar provider and SQLite is perfectly capable of storing up to 8 bytes in INTEGER values, there must be an overflow problem in the Android calendar provider, probably caused by using int instead of long somewhere. If you want to exactly identify or fix this problem, please work with the Android calendar provider source code. It's possible that this bug was introduced with Android 5 or 6.

Edit: the calendar provider uses android.text.format.Time (which is deprecated) to check/fix all-day date/time values. Its documentation states:

For historical reasons when performing time calculations all arithmetic currently takes place using 32-bit integers. This limits the reliable time range representable from 1902 until 2037.

So, only dates between 1902 and 2037 will be processed correctly and it's really a 32-bit problem.

To fix the problem, Android calendar provider would just need to use java.util.Calendar instead of android.text.format.Time. I have created an Android bug report for this: https://code.google.com/p/android/issues/detail?id=225154

Wow, nice Debugging. Thank you for the detailed insight and the report to the Android bugtracker.