On February 8 2015, patch 2.0.0 introduced the Daily Bonus feature: from this date, every 3 days the bonuses "2x Items Drop", "2x Recruit Rate" and "No bonus" alternate in preset chapters;

Double Drop (DD) bonuses affect chapters whose number end with a certain offset, like 3 and 8 (chapters 3, 8, 13, 18, 23, ... ) or 5 and 0; the complete list is to be found below.

Note: The numbers you read under the "Day" column are just indexes, not the number of the day a bonus takes effect (i.e. the "Day 1" bonus happens the day after the number 15, not on the first day of each month).

Day		Chapters with 2x Bonus
1	-
2	Items	2, 7, 12, 17, 22, 27, 32, 37
3	Monsters	4, 9, 14, 19, 24, 29, 34
4	-
5	Items	3, 8, 13, 18, 23, 28, 33, 38
6	Monsters	5, 10, 15, 20, 25, 30, 35
7	-
8	Items	4, 9, 14, 19, 24, 29, 34
9	Monsters	6, 11, 16, 21, 26, 31, 36
10	-
11	Items	5, 10, 15, 20, 25, 30, 35
12	Monsters	2, 7, 12, 17, 22, 27, 32, 37
13	-
14	Items	6, 11, 16, 21, 26, 31, 36
15	Monsters	3, 8, 13, 18, 23, 28, 33, 38

Q: Why does the homepage show Bonuses for UTC/GMT +13 and -11?

A: Because Daily Bonuses are exactly what they are, Daily: they provide you different benefits based on your device's timezone, so changing it allows you to make them last twice longer (setting it to UTC+13 the day before they should begin and to UTC-11 the day after gives you a | 13 + 11 | = 24 extra hours under that bonus) and that's the reason why the starting time printed is the "UTC+13" midnight and not yours :)

If needed, you can change the "lower" (default UTC-11) and the "upper" (default UTC+13) timezones from the Settings menu.

You can read below how to change the timezone on your iOS/Android device.

Q: How do I change the timezone of my device?

on iOS

From the official support page:

1. Make sure that you have the latest version of iOS.
2. Turn on 'Set Automatically' in Settings > General > Date & Time. This will automatically set your date and time based on your time zone.
3. Make sure that your time zone is set correctly. Tap Settings > General > Date & Time > Time Zone.
4. If you still have issues setting your date, time, or time zone, you can turn off Set Automatically in Settings > General > Date & Time and manually set the time and time zone. Or contact your carrier.
5. The option to turn on Set Automatically might not be available with all carriers or in all countries.
6. If the time on your iOS device is wrong after you sync it with your computer, your computer's time might be wrong. Check the time on your computer in System Preferences > Date & Time. You might want to select "Set date and time automatically."

on Android 4.0 (or later)

from the official support page:

1. Open your device's Settings app "Settings" (nd Silver: the "Gear" icon).
2. Touch Date & time.
3. Uncheck Automatic date & time or Automatic time zone.
4. Enter the date, time, or time zone.

on Android (older version)

1. your problem.