For most of the history of Social Security, all monthly payments of benefits came out on the third of each month. That changed in 1997 so that the Title II payments come out on three dates each month. The date you receive your payment depends upon the day of the month upon which you were born.
The Social Security Administration's statement at the time this change was made gives an insight into the level of service that was then prevalent at the agency. This is from a notice published by Social Security in the Federal Register on February 11, 1997 (emphasis added):
SSA’s current practice of paying 47
million beneficiaries within the first 3
days of each month results in a large
surge of work during the first week of
each month. This surge includes a large
number of visitors to field offices and
calls to our toll-free 800 number to
report nonreceipt of a check, question
the amount paid, or ask about other
payment-related issues. Approximately 9 percent of all calls during check week
concern nonreceipt, compared to 3
percent during the rest of the month. As
an example of the surge that occurs
around the current payment days, on
April 3, 1995, 1,091,282 calls were
placed to SSA’s 800 number. On April
14, 1995, the number of calls placed to
our 800 number decreased to 229,022.
It is important to beneficiaries and
customers to be able to reach SSA with
fewer busy signals, and we have
pledged to enable callers to get through
to the 800 number within 5 minutes of
their original attempt. However, in fiscal
year (FY) 1994, during peak periods,
customers encountered busy signals on
SSA’s 800 number 40–63 percent of the
time and had to wait more than 5
minutes to get through about 30 percent
of the time. ...
Our goal is for our customers to have
minimal waits for service when visiting
a Social Security field office. Today,
SSA does not always meet this goal. In
FY 1994 there were 24 million visitors
to our field offices. While the average
wait during check week for individuals
with an appointment was 8 minutes,
some individuals with appointments
had to wait over 2 hours. Thirty-two
percent of the visitors to our offices
without appointments in FY 1994
(typically people who have questions
related to their payments or who want
to report payment delivery problems)
had to wait more than 30 minutes after
arriving to be served. The average wait
during check week for individuals
without appointments was 16 minutes,
although some individuals without
appointments had to wait over 3 hours. ...
The agency already felt it was under customer service stress way back in 1997 but the level of stress was vastly less than it is now. Adequate service has been defined downward dramatically since then.