My understanding of dependent origination is that it asserts that all things are empty of inherent existence. On an intellectual level I can appreciate and accept this however I struggle when it comes to time. Is time included in this? Is it dependent on something else and if so what kind of things are conditions for time? In my mental picture of the world time is kind of a backdrop for everything else but clearly this mental picture conflicts with dependent origination.
Understanding time is an important part of insight into the nature of things. How can you understand the empty nature of entities if you don't understand their relationship with time? How can you be free of self, of the dictate of the form, if you don't see beyond time?
In traditional literature this topic is famously addressed by the founding father of Japanese Zen, Master Dogen, in his essay U-ji - usually translated as "Being-Time" or "Existence-Time". While I would not give justice to it here by quoting or paraphrasing, here are my own limited glimpses of understanding:
Time is not a container. Entities do not "move" through time. Nor the time "moves" while entities "stay in place and age on". Instead, time is existence itself, time is not separate from the state of things. Because entities are empty they do not have an identity that would be retained and would pass from one moment of time to the next. That identity is a conceptual overlay. If you think of transformations like wood=>ashes or milk=>yogurt it becomes very clear. At what point does wood stop being wood and becomes ashes? At what point milk dies and yogurt is born?
...There cannot be such thing as time travel, because the notion of travel itself requires time for the travel to occur in. If you could skip through time, what time would that skipping occur in? Thinking in terms of entities moving through time is a deep-ingrained samsaric thinking.
All compound things exist in some configuration in one point in time, and in a different configuration in another point. Consciousness (awareness) exists as part of that same setup. It looks like it changes, but just like everything else, it just exhibits different configuration at different points in time-space. All phenomena exist as a web of connections across time and space.
Ultimately, Time exists only conceptually, i.e. as a mental formation. Thinking about past, present and future are mental events, happening in the present moment.
We live only for one thought-moment at a time (momentary death).
The mind might be chasing after some object or running away from another object but that also takes place in the present moment, thus we are always in the present moment.
Conventionally, we can speak of Time as existing and exercising some kind of control over beings in conditioned existence. That can be seen in the workings of Kamma. Kamma is fourfold and one of its classifications are called "Time of Ripening"1, i.e. when the kamma is coming into fruition.
There are actions that might produce their effects in this very life, they are called Immediately-Effective-Kamma.
There are actions that might produce their effect in a subsequent life, they are called Subsequently-Effective-Kamma.
Then there are actions that might produce their effects in any life as long as one is in the conditioned realm, they are called Indefinitely-Effective-Kamma.
As seen here Time exists conventionally, as do beings and rebirth, since they are merely concepts, conventions and designations. Ultimately though, these concepts are not findable or inherently existing. In other words they fall under the doctrine of Emptiness (Śūnyatā).
To further illustrate the difference between Conventional and Ultimate reality let's take a look at a quote from the Milindapañhā2 where King Melinda discuss Time with Ven. Nāgasena:
“Nàgasena, when you say, ‘Time immemorial’, what does time mean? Is there any such thing?”
“Time means past, present and future. There are some for whom time exists and some for whom it doesn’t. Where there are beings who will be reborn, for them time exists; where there are beings who will not be reborn, for them time does not exist.”
“Well put, Nàgasena, you are clever in reply.”
As we see here Nāgasena explains that Time exists for beings that will be reborn, i.e. beings that are still wandering in the realm of Samsara.
Time does not exist for beings that will not get reborn, i.e. those who have won Nibbana.
1 Comprehensive Manual of Abhidhamma, Ch. 5: "Compendium of the Process-Freed", p. 201, by Ven. Bhikkhu Bodhi
2 The Debate of King Melinda, Ch. 2: "Rebirth", p. 47, by Ven. Bhikkhu Pesala
I think this answer implies that (passage of) time depends on (two, separated in time) events.
For example 'the time elapsed between today and tomorrow' depends on 'today' and on 'tomorrow'.
Similarly maybe space (a.k.a. distance) depends on (two, separated in distance) objects.
See also this topic which suggests that there have been conflicting opinions/definitions about whether space is conditioned or unconditioned. An argument for its being called unconditioned is that it's eternal (I'm not sure what the word for "eternal" was, I wonder whether it was akalika i.e. timeless).
Time is merely the concept humans use when trying to apprehend impermanence. Time is the measurement of the rate of change of things around us that are appreciable to the scale of which we experience reality. All conditioned things being unable to maintain a constant form, and thus being in constant flux, give the appearance of "time", but there is no time as we conventionally think of it, only constant change, impermanence. Therefore, time is dependent on greed, anger, and delusion, a misapprehension of reality as it is.
The Buddha exclusively used the term 'dependent origination' to refer to twelve conditions that lead to suffering. Once you adhere to the Nagarjuna (Mahayana) view on 'dependent origination' (i.e., cause & effect or conditionality) there will be conflicts since conditionality & the idea of 'no inherent existence' is difficult to apply to all things.
The 'no-inherent-existence' ('emptiness' - 'sunnata') the Buddha was concerned with was the emptiness of 'self', i.e., 'egoism' (SN 35.85). The Buddha was not concerned with the 'no inherent existence' of time since time obviously does not have a 'self', 'ego' or 'personality view'.
Take the laws of nature (dhamma-niyama), which are conditionality, impermanence, unsatisfactoriness, not-self, emptiness, etc. If they lacked inherent existence then they would not exist. How could they be 'lawful'? Even the idea of 'no inherent existence' would have 'no inherent existence'.
The Buddha taught impermanent things naturally cannot be a 'self'. But this does not mean the opposite must apply, namely, permanent things must be a 'self'.
People often ask: "If all things are impermanent, is impermanence itself impermanent?" Naturally, this question is irrelevant since the Buddha only taught conditioned things are impermanent & never taught that impermanence is a conditioned thing. Thus it is reasonable to conclude impermanence is permanent; just as not-self/emptiness (anatta/sunnata) is permanent.
One has to understand that the texts referred to were written in the Iron Age in India. They were not very sophisticated in how they thought about the physical world. For example, they understood it to be made of just 5 elements: earth, water, wind, fire, space. There is no sophisticated discussion of time as a concept. Indeed in the West there is almost no sensible discussion of time until the Enlightenment. Our understanding of time was completely wrong until just a century ago, this year, when Albert Einstein published his General Theory of Relativity.
It's simply unlikely that one will find any satisfactory explanation of time in traditional Buddhist texts.
To complicate things some people (Ñāṇavīra and Buddhadasa) have argued that the Buddha claimed that his dharma was akāliko and that this means that dependent arising cannot be understood in temporal terms. They use the building block approach instead: for example when the walls are present, the roof is able to stay up. When the walls are absent the roof does not stay up (it either cannot be put up or it falls down). The walls must precede the roof in sequence, but the argument is that this does not imply a temporal sequence. I don't find this entirely plausible.
Although the language allows us to talk about time as though it is an entity, this is philosophically untenable. Time is not a feature of the world, it's a feature of how we conceptualise sequences of experiences.
A modern argument would say that time is a Kantian a priori. Like causation, time, is simply a pre-existing concept we superimpose on experience when we observe sequences of events. Hawking argues that the Second Law of Thermodynamics (i.e. entropy increases over time) imposes an direction on time. We can always tell when a film is being played backwards partly because of how we understand causality and partly because of how we understand entropy.
But so what? What soteriological value does this knowledge have? What difference will it make to how you practice or relate to people. None that I can see. The fact is that most of don't need an abstract understanding of time in order to live. If you really want to understand time, then trying to do so in terms of a theory which only seeks to understand how experiences arise in awareness is never going to be very satisfying. There's not a bad description in Stephen Hawking's book A Brief History of Time. Although it is not easy to understand.
I think perhaps that we would need to clarify the purpose of this question. What would one gain by an intellectual understanding of time that is rooted in an Iron Age worldview?
Is it dependent on something else and if so what kind of things are conditions for time?
Time, like any other conditioned phenomena lacks an inherent existence for it also depends on various factors. There's a concept called time dilation from the theory of relativity which shows that time can stretch or shrink depending on the observers and their moving speed relative to each other or the different positions from a gravitational mass or masses.
There is actually concrete scientific evidence that time is empty of inherent existence. This scientific evidence comes from the theory of relativity, together with something about relativity that Einstein himself had not realized. This is the fact that Einstein’s second postulate of relativity — that the speed of light is constant relative to all inertial frames of reference — is not actually a fundamental law of nature but a consequence of the fact that we have defined time in accordance with how we experience the universe.
It is a scientific fact that the rate our body functions is governed by the rate of electromagnetic transmission, since all cells and all organs in our body function via electromagnetism. This means that if we use our conscious experience as the standard for defining our time, we have actually defined time by the rate of electromagnetic transmission, which is the speed of light. That is why the speed of light is always constant — we have actually defined it to be so!
What this means is that we have also defined time according to our conscious experience (which depends on the speed of light). That explains why, in relativity, time distorts depending on the observer's state of motion. Time is thus only an entity that is dependently arisen since it depends on the imputation of the mind that gives it the label “time.” Time does not exist independent of the observer, and hence is empty of inherent existence from its own side. Without the observer, it does not even make sense to talk of time.
A more detailed explanation can be found in my article “Relativity Proves that Time and Space are Empty of Inherent Existence.” http://kenneth-chan.com/physics/relativity-proves-time-space-empty-inherent-existence/. It is probably necessary to look at this longer explanation to fully understand what I am trying to convey. It is just not possible to explain things well in a short answer.
A more mathematical explanation of how time and space are derived from our conscious experience can be found in the paper “Time and Space.” http://kenneth-chan.com/physics/time-and-space/ (This paper was refereed and approved for publication by Professor Kip S Thorne, who is a world authority on General Relativity.)
Please realise that this is concrete scientific proof that the Buddhist Madhyamaka teachings regarding time and space are correct. There are no speculative elements whatsoever in this proof; so even scientists will have to take it into account. Professor Kip S Thorne would not have approved the paper "Time and Space" for publication if the dramatic findings there were based on speculation of any kind.