How to convert time-stamps into human readable form written in a usage-stats file of Android Lollipop?

Question

The file under consideration is any file under /data/system/usagestats/0/daily/. The entries it has are like:

<package lastTimeActive="77497976" package="com.android.settings" timeActive="471657" lastEvent="2" /> 
<package lastTimeActive="50486897" package="com.android.dialer" timeActive="180327" lastEvent="2" />
<package lastTimeActive="83158956" package="com.cyanogenmod.trebuchet" timeActive="461860" lastEvent="2" />
<package lastTimeActive="59444603" package="com.slovoed.oald" timeActive="405608" lastEvent="2" />

Here is the complete text for the file 1438905600000.

The value 77497976 doesn't seem to be Unix Time, and 471657 seems to be milliseconds.

I added that value into the value mentioned in file name i.e. 1438905600000 + 77497976, and the converted resultant of 1438983097976 here doesn't reflect the actual result shown in GUI here:

_{(Click image to enlarge; screenshot was taken on Aug 8, 2015 at 05:08 AM)}

Package name of apps shown in screenshot whose raw time-stamps you can see in the file:

• Settings → com.android.settings
• Dialer → com.android.dialer
• Launcher3 → com.cyanogenmod.trebuchet
• SQLite Editor → com.speedsoftware.sqleditor
• Titanium Backup → com.keramidas.titaniumbackup
• OALD → com.slovoed.oald
• ES File Explorer → com.estrongs.android.pop
• Clock → com.android.deskclock

adb shell su -c 'dumpsys usagestats' is of no help since it gives no output to me.

In Android 4.x, it is easy to understand the time-stamp (mainly the "last time used") because Unix Time is written in the logs, and you can convert it into human readable time easily.

I looked at UsageStats, UsageStatsManager, UsageStatsActivity but couldn't understand how the time gets converted.

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Alternatively, is there a schema which Lollipop follows to write entries in those usage-stats file? Perhaps, that can help to figure out in conversion?

I'm using a rooted OnePlus One running CM12.