The Buddhist teaching about time is closely linked to the doctrine of impermanence. What we see as the passage of time when analyzed in large segments becomes ungraspable when analyzed on the level of single moments of time. Nonetheless, when operating on the ordinary level of discourse, the Buddha taught about the passage of time on both the macrocosmic and microcosmic levels.

Just as all beings are born, grow old, get sick and die, so too do entire world systems come into being, achieve stasis, decay, and cease to be. And every moment of thought can also be seen as coming into being, abiding, decaying, and disappearing.

The length of the process on the level of a world system is called a great aeon, or mahākalpa in Sanskrit. The length of a mahākalpa is calculated as follows: “Starting from a life span of ten years, for every hundred years the age of people increases by one year, and their height increases by one inch. This keeps on increasing until of coming into being, stasis, decay, and emptiness. Those four terms are explained as follows.

A thousand small kalpas together make up a medium-sized kalpa. One medium-sized kalpa covers a period of coming into being. A period of stasis also spans twenty small kalpas, a period of decay is twenty small kalpas long, and a period of emptiness is also twenty small kalpas.

“‘But,’ you say, ‘I can’tpossibly conceive of that long a period of time.’ Well, if you can’t grasp this concept, then I’ll shrink the kalpa down a bit for you to enable you to understand. Let’s discuss the life span of a person. A person’s life span extends for several decades, and those years span the time of being born, the time of growing old, the time of sickness, and the time of death. Those four different periods of time are synonymous with the coming into being, stasis, decay, and emptiness of a world system.

“Then you say, ‘Well, I still don’t understand—I still can’t comprehend this idea.’ Well, we’ll shrink it some more and talk about a single year’s time. A year has four seasons: spring, summer, fall, and winter. Spring is the period of coming into being; summer is the period of stasis; fall is the period of decay; and winter is the period of emptiness.” (FAS Ch5-6 115-117)

Suppose, o monks, there was a huge rock of one solid mass, one mile long, one mile wide, one mile high, without split or flaw. And at the end of every one hundred years a man should come and rub against it with a silken cloth. Then that huge rock would wear off and disappear quicker than a kappa (i.e., kalpa). (SN XV 5, quoted in Trevor Ling, Dictionary of Buddhism, 72)

The Buddha also taught that time is relative to our state of mind; it passes more quickly when we are happy and less quickly when we are unhappy. Therefore, passage of time and life span differs on the different paths of rebirth. (SS II 68-69)

According to Mahayana Buddhist teaching, time is fundamentally unreal and is the product of distinction-making in the mind.

Past thought cannot be got at, present
thought cannot be got at, and future
thought cannot be got at. (VS 124)

“Earlier a disciple asked me, ‘What is time?’ I haven’t any time. There is no time. Time is just each person’s individual awareness of long and short; that is all. If you are happy every day, fifty years can go by and you won’t feel it has been a long time. If one’s life is very blissful, if one has no worries, anxieties, anger, or afflictions, one’s entire life seems but a short time—the blink of an eye. Ultimately, time is nothing more than a distinction based upon each person’s awareness.… (SS II 69)

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