How to add number of days in postgresql datetime

This will give you the deadline :

select id,         title,       created_at + interval '1' day * claim_window as deadlinefrom projects

Alternatively the function make_interval can be used:

select id,         title,       created_at + make_interval(days => claim_window) as deadlinefrom projects

To get all projects where the deadline is over, use:

select *from (  select id,          created_at + interval '1' day * claim_window as deadline  from projects) twhere localtimestamp at time zone 'UTC' > deadline

For me I had to put the whole interval in single quotes not just the value of the interval.

select id,     title,   created_at + interval '1 day' * claim_window as deadline from projects   

Instead of

select id,     title,   created_at + interval '1' day * claim_window as deadline from projects   

Postgres Date/Time Functions

you can just use the below code to append or substract any date field

select date('08/30/2021') + 180 ---it will give next 180 days date

select current_date + 180 ---it will give next 180 days date

select current_date - 180 ---it will give before 180 days date