Hi, everybody. I present you my notes on time of purchase of rings.

Sunrise Morning Light Ring
3 before Sunset Gem Ring
2 before Sunset Demon Ring
1 before Sunset Demon Ring

Sunset Medusa Eye
3 before Sunrise Medusa Eye
2 before Sunrise Cunning Echo
1 before Sunrise Night Ring.

Originally posted by †BOIN†:

Morning Ring - Regen of hp and mp increase by 6%.
Gem Ring - Give 10 extra gold for each monster killed.
Demon Ring - Increase stats by 10%.
Medusa Eye - Reduce 10% damage from monsters.
Cunning Echo - 50% of your damage penetrate monster's armor.
Night Ring - decreases your spell's CDs for each monster killed

And also exact time:

0:00 Morning Light Ring
1:00 Gem Ring
2:00 Demon Ring
3:00 Demon Ring
4:00 Medusa Eye
5:00 Medusa Eye
6:00 Cunning Echo
7:00 Night Ring
8:00 Morning Light Ring
9:00 Gem Ring
10:00 Demon Ring
11:00 Demon Ring
12:00 Medusa Eye
13:00 Medusa Eye
14:00 Cunning Echo
15:00 Night Ring
16:00 Morning Light Ring
17:00 Gem Ring
18:00 Demon Ring
19:00 Demon Ring
20:00 Medusa Eye
21:00 Medusa Eye
22:00 Cunning Echo
23:00 Night Ring
24:00 Morning Light Ring
25:00 Gem Ring
26:00 Demon Ring
27:00 Demon Ring
28:00 Medusa Eye
29:00 Medusa Eye
30:00 Cunning Echo
31:00 Night Ring
32:00 Morning Light Ring
33:00 Gem Ring
34:00 Demon Ring
35:00 Demon Ring
36:00 Medusa Eye
37:00 Medusa Eye
38:00 Cunning Echo
39:00 Night Ring
40:00 Morning Light Ring
41:00 Gem Ring
42:00 Demon Ring
43:00 Demon Ring
44:00 Medusa Eye
45:00 Medusa Eye
46:00 Cunning Echo
47:00 Night Ring
48:00 Morning Light Ring
49:00 Gem Ring
50:00 Demon Ring
51:00 Demon Ring
52:00 Medusa Eye
53:00 Medusa Eye
54:00 Cunning Echo
55:00 Night Ring
56:00 Morning Light Ring
57:00 Gem Ring
58:00 Demon Ring
59:00 Demon Ring
60:00 Medusa Eye
61:00 Medusa Eye
62:00 Cunning Echo
63:00 Night Ring
64:00 Morning Light Ring
65:00 Gem Ring
66:00 Demon Ring
67:00 Demon Ring
68:00 Medusa Eye
69:00 Medusa Eye
70:00 Cunning Echo
71:00 Night Ring
72:00 Morning Light Ring
73:00 Gem Ring
74:00 Demon Ring
75:00 Demon Ring
76:00 Medusa Eye
77:00 Medusa Eye
78:00 Cunning Echo
79:00 Night Ring
80:00 Morning Light Ring