Experienced time is the third currency. It is also the first currency with an unit, and the unit is "second(s)". The unit normally won't be converted to longer timespam. It is earned through prestiging existances.
Each second of experienced time grant 20% bonust to the existivity production multiplicatively, which can be increased using upgrades. The display of the boost is first noted with added percentages to the unbuffed production, but when the boost reaches ×10, it shows by the factor which it is boosting at.
Prestiging existances to experienced time, which is commonly called experiencing, requires 16×2x where x is the seconds of experienced time earned through prestiging(note that it does not include passive production later in the game).
The next prestige is seen at 3 seconds of experienced time, and requires 4 seconds and 450 existivity. At that point, 450 existivity shouldn't be too difficult. Doing so will reset existivity, existance and experienced time, and earn a new currency, a thought.