Purva (पुर्व) means "former" or "earlier." It is not a unit of time or years. In Jain usage, Purva is used to indicate something that happened previously or in the past (for example, Purva kram, Purva jiva meaning past life). It does not specify a numeric duration like years or ages.

If you meant a specific context (e.g., Purva in a particular sutra or verse), tell me the exact line and I’ll explain its meaning in that context.