It is Military slang. It is usually used to refer to any time when the sun isn't up, usually between mid-night and 4 am or so. Most operations start at Oh dark thirty, much earlier than a normal 'person' would think civilized.

[New]

0-Dark-30 is 30 minutes before sunrise.

-Edit-

0-dark-30 refers to a time (any time really) where the sun isn't up, but you are(and you're probably working). It doesn't mean military, but generally this is when Military members have a lot of work, so it applies well to them.

It is Military slang. It is usually used to refer to any time when the sun isn't up, usually between mid-night and 4 am or so. Most operations start at Oh dark thirty, much earlier than a normal 'person' would think civilized.

[New]

0-Dark-30 is 30 minutes before sunrise.

-Edit-

0-dark-30 refers to a time (any time really) where the sun isn't up, but you are(and you're probably working). It doesn't mean military, but generally this is when Military members have a lot of work, so it applies well to them.

The ISBN of Dark Challenge is 0-505-52409-0.

The ISBN of The Dark Beyond the Stars is 0-312-86624-0.

The ISBN of "Dark Demon" by Christine Feehan is 978-0515139751.