How to determine the end of a meditation session without a clock?

To refer to the traditional way that time is kept:

"The best way I've heard to a) keep track of time b) without a clock (or timer) was related to me by my 91-year-old teacher who said in the old days they used to use incense sticks; once the incense stick was finished, they would switch from walking to sitting. For shorter sessions, you could cut the sticks in half, etc. Of course, it still means you need to open your eyes every so often during sitting." --this answer

The act of not timing your sitting is a profound one. It's not like the Buddha timed his sittings when he attained Enlightenment! After nourishing himself the Buddha himself literally said "I will not get up from this Bodhi tree until I attain Awakening! Let my bones break and my flesh rot before I shall arise." And then he entered the 1st jhana, 2nd jhana all the way to 4th and then experienced the 4 formless absorptions one by one and then attained Awakening.

He did not time his sittings except taking a bit of a break when he was truly exhausted and he opened his eyes to look at the night sky to take a bit of a rest. And like magic, right then, he Awakened.

[Similarly Zen practitioners and other "hardcore" practitioners do not time their sittings... and they tended to Awaken when they took a bit of a rest and their Buddha Nature spotaneously opened to them, their skandhas dropping away giving them a strong taste of Awakening.]

Thus, the ultimate "inorganic" method is your own physical exhaustion, your own body telling you it is time to take a break from your arduous efforts!

Nonetheless, You can use other similar methods that are "organic" and do not use digital devices: tea kettle boiling, the birds starting to chirp in the morning as you push your meditation on in the early morning, etc.

Also your question is an important question because we all need to do an electromagnetic detox! We are all heavily dependent on our devices and are sleeping, reading, and practicing in a pool of EMR. I definitely notice a huge difference when I wear my crystals than when I am not. Many of us experienced times when we go to a garden or some greenspace, far away from wifi connections and our mind completely clears and it feels the bliss of concentration is close at hand. It is also much easier to think about one's own life and contemplate in such an environment, also due to having less electronic devices subconsciously yelling and calling us in hundreds of ways.

The best thing to do is just do it as long as you feel it. Once your mind starts emerging, you're done. I've never understood people who try to turn it into a marathon, seeing how long you can go. That's totally counterproductive. Once you feel like getting up, get up.

Alternately stare at a clock. That might sound like a joke, but you've got to stare at something. The tension and tediousness of staring at a second hand going round and round is bound to be useful in breaking through to release.

I don't recommend listening to music. That also defeats the purpose. Also, don't overthink it. Make sure you're not using the question of how to time your sessions as an excuse not to do them.

I use an APP called Meditation Helper. It is very useful. I has a nice bell sound. You can program the total time and also interval times. I also like the "reminder" function that you can program, the App will remind you to meditate every day.

I use the meditation timer app and its very useful! I usually have meditation time set for an hour, and a mild bell to ring every five minutes, every few bells or so ill switch to walking or sitting. I'm still trying to solidly make it a full five minutes of absolute mindfulness without drifting off or zoning out but... maybe next time... hah. but yeah, after it goes off a few times you'll lose track and then its just a reminder and/or starting point or you can set it to go off anywhere from every one minute to 2, 3,4,5,6... etc all the way to 24 hours (or not to go off until the time is up) so yeah, i second that recommendation!

I can only say what helps me. I usually have recorded tracks of music playing (like chanting to Quan Shi Yin, Amitabha, or loving-kindess chanting) and I stop when the track is over. I have tried using a bell, but, for me, often the anticipation of the bell might as well be as distracting as looking at a clock.

At first I did what you are trying to avoid and checked the clock on the wall. Then I used an electric kitchen timer; this was effective, but the alarm was unpleasant. Thus I switched to the pre-installed timer on my Android device for a while and did fairly well, but it does not have the ability to set up multiple meditation periods.

Now I'm using an Android app called Zazen Meditation Timer. I chose it because it required no special permissions, where all the others I investigated required permissions which I did not think a meditation timer needed and which I did not want to grant. It allows the user to set up different meditation "sessions" (e.g. weekday 20 minute sit, weekend hour & one half sitting and walking). Each session can have different periods (e.g. 30 minutes sitting, 15 minutes walking, 30 more minutes sitting).

Some sources sell dedicated meditation timers. Many can be easily found on the World Wide Web via the search engine of your choice.

Edit to mention a couple things I initially forgot:

I also have a CD I got during a retreat. It features gongs, bells, and other summoning sounds, followed by a starting bell. There there are 20 minutes of silence, followed by a bell to mark the end of a 20 minute meditation period. It has other chants, gathas, etc. and then another 20 minute meditation period, followed by some ending chants.

Also, while a lot of the things you'll find searching for "meditation" on Youtube are lengthy musical pieces that may be more appropriate as background music, there are guided meditation sessions, if that's what you're seeking.

If you burn incense sticks, you can train your mind to pick up the smell of cold ashes when the stick has finished burning.

Best is to use Adhitthana. Initially this might not be perfect but over time it becomes accurate. When you sit make a strong determined though that you will meditate for a particular time period.

I use a wind-up kitchen timer. Because it is low-tech, it works better for me than a smartphone app, which has a subtle distracting effect due to being an open-ended device. I do make sure to have no clocks in sight. In the zendo we used to have a giant pendulum clock, which ticked loudly and chimed every 15 minutes. That had its charm too :)

Another way to keep time is to count breaths on phalanges of hands, with the thumb. 3 phalanges times 4 fingers makes 12. 12 on one hand times 12 on the other makes 144 (breaths). This is about 25-30 minutes, depending how you breath.

Having to look at a clock every few minutes really defeats the purpose!

Have you ever tried telling yourself to wake up at a certain time before you sleep? I can tell you from personal experience that it works.

My meditation teacher asks us not to use any clock. She asks us to train ourselves to emerge from meditation at specified time without external help. I haven't really tried it yet (except for waking up from sleep), and the teacher will always ring the bell in our group sitting despite her advice :).

After all, one of the jhana mastery is the ability to remain in jhana for exactly the pre-determined length of time.

A meditator should first master the lower jhānas, before they can go into the higher jhānas. There are five aspects of jhāna mastery:

1. Mastery in adverting: the ability to advert to the jhāna factors one by one after emerging from the jhāna, wherever he wants, whenever he wants, and for as long as he wants.
2. Mastery in attaining: the ability to enter upon jhāna quickly.
3. Mastery in resolving: the ability to remain in the jhāna for exactly the pre-determined length of time.
4. Mastery in emerging: the ability to emerge from jhāna quickly without difficulty.
5. Mastery in reviewing: the ability to review the jhāna and its factors with retrospective knowledge immediately after adverting to them.

The best way I've heard to a) keep track of time b) without a clock (or timer) was related to me by my 91-year-old teacher who said in the old days they used to use incense sticks; once the incense stick was finished, they would switch from walking to sitting. For shorter sessions, you could cut the sticks in half, etc. Of course, it still means you need to open your eyes every so often during sitting.

I often suggest meditators just to look at the clock every so often; it's not really that big of a deal with insight meditation, since the concentration is momentary anyway. It can be a good exercise in patience watching how often your mind wants to check and see if you're finished yet :)

Eventually, as someone said, your mind can estimate pretty well how long you've been sitting and you'll find yourself checking the clock (or incense stick) just when it's time to finish.

If you have a smartphone, consider using a meditation timer app for keeping track of sessions. Simple ones like Meditation Helper (Android) or Meditation Timer (iPhone) are free and do the simple job of keeping the time, ringing a bell when finished. This cen perhaps let you just focus on the meditation for the entire session.

Note: I only have experience with the Android Meditation Helper, which is why the link is provided. It has reminders and a log, quite simple.

UPDATE regarding the use of timers and bells:

Using a meditation timer can be beneficial, especially for beginners, where hearing repeated bells at intervals (starting out as frequent as 2 minutes, increasing to 5, then 10, and so on) can work as a reminder to gently return to the meditation object. However, there is a point where the bells become a hindrance, where they may disturb a deeper meditation, so the recommendation is to phase out the use of the bells.

Meditate for as long as you can, each time. Only if you have limited time for a setting, then use the bell as a reminder. The app works well for this, where you can first set the bells at intervals, then to end the session. If you only look at the meditation timer (locking the screen during meditation) after the meditation session has ended, you can use it to evaluate the session. You may find that sometimes a 30 minute meditation can be challenging, and other times you're surprised to find that an hour and a half passed while in deep meditation.