Actually TPM's do have a secure clock. There's just no guarantee about when it will keep ticking. You can detect if it gets reset because there is a 20 byte nonce, which changes at every reset. I've found that my HP laptop preserves the timer in S3 sleep, I don't know for sure, but I shut it down for a few seconds and it seemed to be preserved, which was a surprise. And my HP desktop system is never shutdown, but it preserves the timer across reboots.

If bcflick eetects a timer reset, it won't let you spend anything for 24 hours. But you can always boot into a safe mode and reset your passphrase. This will reininitialize bcflick and you can spend up to the daily limit, right away.