Recent research seems to suggest that mindfulness practice can alter your perception of time. The investigators were investigating the hypothesis that the moment-to-moment awareness that is encouraged by mindfulness meditation practice would have the subjective effect of slowing down time , such that short periods of time seemed longer. And that was exactly what they found.
The researchers used a temporal bisection task, which allows researchers to gauge where each individual subjectively splits a period of time in half. Participants' responses to this task were collected twice, once before and then again after a listening task. By separating participants into two groups, respondents listened for ten minutes to either an audiobook or a meditation exercise designed to focus their attention on the movement of breath in the body. The results showed that the control group (audiobook) didn't change in their responses after the listening task compared with before. However, mindfulness meditation led to a relative overestimation of durations i.e. time periods felt longer than they had before.
One interesting feature of this study was that the participants received very little training or experience of mindfulness meditation - just 10 minutes, as opposed to months or years of training. This suggests that the internal clock modulation found in this study is relatively sensitive to short meditative states, and does not require a large degree of training to access it. That seems pretty remarkable to me, and the effects could be leveraged into treatments for difficulties that may distort the effects of time, such as addictions, memory, and emotional regulation.