How to get date in Julia

You can now use:

julia> Dates.today()
2015-07-15

julia> string(Dates.today())
"2015-07-15"

Your exact sketch now works precisely as you've written it after using Dates. The Dates module is a part of the standard library and thus is available by default:

julia> using Dates

julia> today()
2020-08-20

julia> string(today())
"2020-08-20"

(note: this answer has been edited and updated for version 1.0+; this question pre-dates the existence of the Dates stdlib.)