Usually each story is assigned its place in a feed in accordance with its timestamp. But it is absolutely possible that two stories will have the same timestamp, so the position becomes ambiguous. To make the feed work properly, we need to be able to define the order of stories and specify a position in the feed to within a particular story.
To achieve this goal, each story is assigned a moment, which is calculated as follows:
moment = timestamp * 100 + seq
seq here is an arbitrary number from 0 to 99 that is chosen by the
node to make the resulting value unique.
Moments larger or equal to 9⋅1015 are assigned to “pinned” stories.