Bitshares - "coin days earned"

What are "coin days earned" when you become a lifetime member of bitshares? Coin days earned are simply days accumulated towards your vesting balance. Most vesting balances are able to withdraw immediately, but some require a 90 day vesting period. Hope this helps someone, please give me an upvote if so. Join the Bitshares Exchange today via my community https://wallet.bitshares.org/?r=nuts2727