Rails 4.2: datetime attribute not being saved -

i'm using attribute named :subscription_active_untill in user table, type datetime, i'm trying save datetime stamp in not being saved. example, executing current command in rails console

user.find(3).update(:subscription_active_untill => 1473363930) 

it returns true in console when see record using user.find(3) :subscription_active_untill attribute still nill. issue?

note: can update other attribute of same record without issue, problem specific attribute.

the issue has been solved, above trying save wrong format datetime (i.e. unix timestamp format). had convert correct format. so, doing following commands saves attribute correctly.

user.find(3).update(:subscription_active_untill => 2016-09-08 20:14:30 utc) 

to convert unix timestamo utc format can use following code:

time.at(1473363930).utc