Hint: Time
The answer to this puzzle is:
1. PAST
2. JANUARY
3. HOUR
4. SEASON
5. FOUR
6. AUGUST
7. MONTH
8. SIX
9. SECOND
10. JUNE
11. DUSK
12. ELEVEN
13. ETERNITY
2. JANUARY
3. HOUR
4. SEASON
5. FOUR
6. AUGUST
7. MONTH
8. SIX
9. SECOND
10. JUNE
11. DUSK
12. ELEVEN
13. ETERNITY