2 of 2 added 57 characters in body

Stax, 54 bytes


Run and debug it

Here's the unpacked, ungolfed, ascii representation of the same program.

                            stack starts with total seconds
c60/                        push total minutes to stack
c60/                        ... hours 
c24/                        ... days
Yc7/                        ... weeks
y31/                        ... months
y365/                       ... years
L                           make a list out of all the calculated time units
`)sQP(dr'pk,oV4?_HIFD?x`j   compressed literal for singular forms of unit names
\                           zip totals with names
rF                          foreach pair of total and name (in reverse orer)
  h!C                       skip if the current total is falsey (0)
  _J                        join the total and unit name with a space
  's_1=T+                   concat 's' unless the total is one

Following execution, since there's no other output, the top of the stack is printed implicitly.

Run this one