Can RRule descirbe an event that occurs at two specific times each day?

Question

Let's say I have an event that occurs at 7:00 and 2:00pm each day. The RRule would look like this:

FREQ=DAILY;BYHOUR=10,14

If I wanted an event that occurs at 10:00am and 2:30pm, I would assume it would look like this:

FREQ=DAILY;BYHOUR=10,14;BYMINUTE=0,30

But this doesn't seem to be correct. The spec says that "BYxxx rule parts for a period of time less than the frequency generally increase or expand the number of occurrences of the recurrence". Testing this at http://jkbrzt.github.io/rrule/ produces the following:

• Mon 10:00
• Mon 10:30
• Mon 14:00
• Mon 14:30
• Tue 10:00
• Tue 10:30
• Tue 14:00
• Tue 14:30

What I really want is this:

• Mon 10:00
• Mon 14:30
• Tue 10:00
• Tue 10:30
• Wed 10:00
• Wed 14:30
• Thu 10:00
• Thu 14:30

Answer 1

I figured out I could make this work using BYSETPOS:

FREQ=DAILY;BYHOUR=10,14;BYMINUTE=0,30;BYSETPOS=1,4

If you wanted 10:30am and 2:00pm, you'd use:

FREQ=DAILY;BYHOUR=10,14;BYMINUTE=30,0;BYSETPOS=2,3

The recurrence instances will be in chronological order, so, the order of BYMINUTE has no effect on BYSETPOS. To demonstrate, if we remove BYSETPOS, both of the above rules will yield the following instances for each day:

╔═══╦══════╦════════╗
║ P ║ Hour ║ Minute ║
╠═══╬══════╬════════╣
║ 1 ║   10 ║     00 ║
║ 2 ║   10 ║     30 ║
║ 3 ║   14 ║     00 ║
║ 4 ║   14 ║     30 ║
╚═══╩══════╩════════╝

So in the first case, we're selecting instances 1 and 4, and in the following case we're selecting instances 2 and 3.

Note that this only works if DTSTART uses the first BYHOUR/BYMINUTE values (10:00am in the above cases).