This apparently means that the 24th of January will be the most depressing day of the year,

Where W is weather, D is debt – minus the money (d) due on January’s pay day – and T is the time since Christmas. Q is the period since the failure to quit a bad habit, M stands for general motivational levels and NA is the need to take action and do something about it.

I think it’s flawed, what about, DH days till holiday, and TM number of cups of tea made ?