Here’s a quick tip for BigFix users… Want to know when a computer first checked into your deployment? Try creating a new global property:

First Check-in = subscribe time of current site
have it evaluated every 30 days
(this value doesn’t change so keep the impact on your deployment as minimul as possible…)

Thanks to the BigFix forum: http://forum.bigfix.com/viewtopic.php?id=1801