Do NOT use the mobile app to bid or do anything important.
Even on the website the countdown is not an accurate measure of how much time you have to submit a bid for it to be timely. The bid (data sent when you click the confirm button) must be received and timestamped at eBay's servers before the end of the last second of the auction. The countdown is a script that runs on your device that calls for updates about every 3 seconds (and not all updates are succesful) and uses the "time left" returned by eBay (which is accurate as of the time eBay processes your request) to use your device's clock to count down from that. So it's slow by the lag between eBay and your device's display AND slow in that there's a lag between that display, your nervous system, your device, your network and ISP, and the internet back to Salt Lake City and to an eBay server and in that server to give the timestamp.
There used to be a static time left display on the Bid History Page that one could use to synch a local clock taking into account the various lag times, but it is now dynamic (i.e. uses the script to make it a countdown). To snipe an important item it is best to use one or more snipe services instead of or as a backup to trying to guess how much of a buffer you need on the countdown.
