Seeing as the StellarSky makes it so that the days get longer and shorter over the course of the year (as configured by: D:Year_Length=365 …

…it would be extremely informative (critical) for the user to have the option (by config, or menu activation) to display on the screen somewhere (top left or right, small) the following information:

-Current Day & Year Length (ie Day 272/365) (note: March 20 = Day #1, June 20 = Day #92, September 23 = Day #187, December 22 = Day #277)
-Current Season (ie "Winter")
-Day Length (in HH:MM format & Ticks)
-Night Length (in HH:MM format & Ticks)
-Wake-up Time (in HH:MM format & Tick #)
-Sleep Time (in HH:MM format & Tick #)

Hmm.. what do you mean by 'Wake-up Time' and 'Sleep Time'?

Is Sleep Time and Wake time based on light levels? Or are they hard-coded times like in Vanilla?

Sleep time is based on light levels. Wake time is hardcoded.

Okay cool. I thought so. In that case, if it will be hard to predict Sleep Time, don't worry about adding a feature to display it. It's not necessary, or critical.

It would be on HUD, and can be enabled/disabled by a key. Is this okay?

The time of day (hh:mm) that the player can begin sleeping, and will wake up.

Or are those two values constant throughout the year?

That one would be hard to predict, but I'll try.
EDIT: I think it is hard to achieve. Sorry.
Showing Current Day/Year Length and Season, Time would be added on next 1.7.10 update.

Added in v0.1.13[1.7.10] update.

That sounds perfect!

The gui "Time" debug info displays the Time based on IRL minutes… but what I was thinking of was Time that displays the in-game "Time of Day"… from 12:00am (Midnight) to 12:00pm (Noon) to 12:00am (Midnight).

For example:

Time: 3:15 pm

So there might be configs for that. (Please reopen this issue)

I don't think I can re-open it, I think you have to.

What do you mean there might be configs for that?

Found it. It's in the client's config.

I:Hour_Length=60
D:Minute_Length=20

To get a proper DayTime value the, client needs to be set to:

D:Minute_Length=16.6666

(maybe you want to change the default setting to 16.6666)

Also, can you change the format so that it has leading zeroes in it? Right now… 06:08 am shows up like 6:8, for example.

It would be much easier to read if it was in the HH:MM format with Leading Zeroes.

Something like length of hour and minute.

Check it out: http://imgur.com/cSpoVmS Mine doesn't show 6:08… it shows 6:8.

Oh I'd fix that. I thought it is shown as 06:08 format.
EDIT: Actually it is 6:08 format. Do you want something like 06:08 AM? Then I'd implement that.

The GUI is always ON by default when we start Minecraft. Can you make it OFF by default (like the F3 hud), and must be activated by the user using their hotkey?

Ah, I'd also implement those features.
& Something is messed with the numbering.. It shouldn't be shown as 6:8.

Implemented on v0.1.15.

Thanks for the great request! It will be accepted on v0.1.10