I was wondering if their a easier way to look up post date by year and month instead of days because It would probably be tedious for me to update the search every time. I tried date:**** and date:****-** but It doesn't work that way.I know there are years tags which tell when it was created but not when it was submitted. is there something else I could try?

where you search, there's a 'search options' link, that'll take you to https://e621.net/help/show/cheatsheet -- which will give you the context

SnowWolf already gave you the tools needed above, however most date metatags are for searching specific amount of time from current day. What you need is ranges.

date:2016-01-01..2016-12-31 will give you all posts posted here in 2016. (does look like bit monster of a tag, but will only count as single tag search so don't worry)
date:2016-01-01..2016-01-31 will give you all posts posted here in January 2016.
date:year..year would look up posts from exactly year from now and give you all posts within year from that time.
2016 will give you all posts which are signed, created or initially publicized in 2016.

Year tag like 2016 is needed to be put manually so it's not as accurate as metatag for uploading date, however this way you will get year 2016 posts even if they were posted in 2017, e.g. if some post was updated with better version. You can however simply also search deleted posts when looking up upload dates from 2016 with adding status:any, this way every time you see deleted post, you can open it and see if reason has been for the post to be inferior or if the post had any sources to go to.

Not sure would it be possible to ask that if you searched with date:2016 that it would automatically know you to mean date:2016-01-01..2016-12-31 without needing to type it out.