Odd datetime representation in Quickbooks My Time files

Question

I'm attempting to process Quickbooks My Time imt files using PHP. The imt file is a plaintext XML file. I've been able to use the PHP SimpleXML library with no issues but one:

The numeric representations of datetime in the My Time XML files is something I've never seen before:

<object type="TIMEPERIOD" id="z128">
    <attribute name="notes" type="string"></attribute>
    <attribute name="start" type="date">308073428.00000000000000000000</attribute>
    <attribute name="running" type="bool">0</attribute>
    <attribute name="duration" type="double">3600</attribute>
    <attribute name="datesubmitted" type="date">310526237.59616601467132568359</attribute>
    <relationship name="activity" type="1/1" destination="ACTIVITY" idrefs="z130"></relationship>
</object>

You can see that attritube[@name='start'] has a value of:

308073428.00000000000000000000

This is not Excel based method of storage 308,073,428 is too many days since 1900-01-00 and it isn't Unix Epoch either.

So, my question is, has anyone ever seen this type of datetime representation?

Answer 1

It looks like Quickbooks My Time imt is using some version of OS X Core Data to store the application information. After digging around for awhile, I found that Core Data/Cocoa uses 2000-01-01 00:00:00 as the start time for their epoch. Therefore, it's simply a matter of adding the seconds to the epoch to get the correct date:

<?php
  $start_as_int = (int) $node;
  $dt = new DateTime('2010-01-01 00:00:00');
  $dt->add(new DateInterval('PT'.$start_as_int.'S'));
  print $dt->format('m/d/Y');
?>

This is good enough to get the correct date, however, I'm still not certain how to process the values to the right of the decimal point for a valid time.