the first of january since or for

We often use for and since when talking about time.

for + period: a "period" is a duration of time - five minutes, two weeks, six years. For means "from the beginning of the period to the end of the period".

since + point: a "point" is a precise moment in time - 9 o'clock, 1st January, Monday. Since means "from a point in the past until now".

Look at these examples:

for
a period
from start to end since
a point
from then to now
>===< x===>|
for 20 minutes
for three days
for 6 months
for 4 years
for 2 centuries
for a long time
for ever since 9am
since Monday
since January
since 1997
since 1500
since I left school
since the beginning of time
all tenses perfect tenses
for
For can be used with all tenses. Here are a few examples:

They study for two hours every day.
They are studying for three hours today.
He has lived in Bangkok for a long time.
He has been living in Paris for three months.
I worked at that bank for five years.
Will the universe continue for ever?
We do not use for with "all day", "all the time":

I was there all day. (not for all day)
since
Since is normally used with perfect tenses:

He has been here since 9am.
He has been working since he arrived.
I had lived in New York since my childhood.
We also use since in the structure "It is [period] since":

It was a year since I had seen her.
How long is it since you got married?