My apologies. I normally document what I did a lot better but I was in a rush. Here's how I came to those numbers from the excellent description of the problem you gave. As usual with me, the details are in the comments in the code below...

/*************************************************************************************************

To give some details.

1. Quartz.Net stores its time values in a bigint.

2. The value is the column is the number of ticks that have elapsed since January 1, 0001 12:00am.

3. All ticks values are UTC date time values

4. There are 10000 ticks in a millisecond.

5. For example November 24, 2010 16:30 would be 634262130000000000

*************************************************************************************************/

--===== Here's the first number

SELECT MillisecondsPerDayTimes10000 = DATEDIFF(ms,'19000101','19000102')*10000.0

--===== If we divide the number of ticks for November 24, 2010 16:30

-- by the number of ticks per day (the first number), we end up

-- with a "Date Serial Number" where the whole numbers represent

-- the number of days since the January 1, 0001 12:00am epoch. The

-- decimal places represent the partial day which is also known

-- as the "Decimal Time".

SELECT Epoch1DateSerial = 634262130000000000/(DATEDIFF(ms,'19000101','19000102')*10000.0)

--===== Although SQL Server's DATETIME datatype is represented by two

-- 4 byte integers, they are most correctly interpreted using a

-- float conversion thusly...

SELECT Epoch2DateSerial = CAST(CAST('November 24, 2010 16:30' AS DATETIME) AS FLOAT)

--===== Since both Date Serial Numbers are for the same date and time,

-- (November 24, 2010 16:30), simple subtraction gives us the second

-- number which is the correction factor to convert one epoch to

-- the other as a number of days.

SELECT CorrectionFactorDays =

634262130000000000/(DATEDIFF(ms,'19000101','19000102')*10000.0) --Epoch1DateSerial

- CAST(CAST('November 24, 2010 16:30' AS DATETIME) AS FLOAT) --Epoch2DateSerial

--===== Finally, we make the simple substitutions to come up with the

-- simple formula to make the conversion to produce the correct

-- Date Serial Number from the number of ticks and convert that

-- Date Serial Number to an SQL Server DATETIME datatype and

-- we're done.

DECLARE @Ticks BIGINT

SELECT @Ticks = 634262130000000000

SELECT CAST(@Ticks/864000000000.0 - 693595 AS DATETIME)

For those that don't know what an "Epoch" is...

http://www.merriam-webster.com/dictionary/epoch