How to Get the Last 12 Months from the Current Date

var theMonths = new Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December");var now = new Date();
for (var i = 0; i < 12; i++) {  var future = new Date(now.getFullYear(), now.getMonth() + i, 1);  var month = theMonths[future.getMonth()];  var year = future.getFullYear();  console.log(month, year);}

SQL : Extract last 12 months of data from SQL server when period is in the format of yyyymm

You can use the following query:

SELECT *
FROM YourTable
WHERE [A header] >= YEAR(DATEADD(month, -12, GETDATE())) * 100 + MONTH(DATEADD(month, -12, GETDATE()))

db<>fiddle

This is made worse by the fact you are storing dates as integers. Instead you should store the last day of the month as a date type, then you can do

WHERE [A header] >= DATEADD(month, -12, GETDATE()))

find start and end date of previous 12 month from current date in python

You can use current_date.replace(day=1) to get first day in current month.

And if you substract datetime.timedelta(days=1) then you get last day in previous month.

And you can use again replace(day=1) to get first day in previous month.

If you repeate it in loop then you can get first day and last day for all 12 months.

import datetime

current = datetime.datetime(2022, 5, 5)

start = current.replace(day=1)

for x in range(1, 13):
    end   = start - datetime.timedelta(days=1)
    start = end.replace(day=1)
    print(f'{x:2} |', start.date(), '|', end.date())

Result:

 1 | 2022-04-01 | 2022-04-30
 2 | 2022-03-01 | 2022-03-31
 3 | 2022-02-01 | 2022-02-28
 4 | 2022-01-01 | 2022-01-31
 5 | 2021-12-01 | 2021-12-31
 6 | 2021-11-01 | 2021-11-30
 7 | 2021-10-01 | 2021-10-31
 8 | 2021-09-01 | 2021-09-30
 9 | 2021-08-01 | 2021-08-31
10 | 2021-07-01 | 2021-07-31
11 | 2021-06-01 | 2021-06-30
12 | 2021-05-01 | 2021-05-31

EDIT:

And if you use pandas then you can use pd.date_range() but it can't for previous dates so you would have to first get '2021.04.05' (for MS) and '2021.05.05' (for M)

import pandas as pd

#all_starts = pd.date_range('2021.04.05', '2022.04.05', freq='MS')
all_starts   = pd.date_range('2021.04.05', periods=12, freq='MS')
print(all_starts)

#all_ends   = pd.date_range('2021.05.05', '2022.05.05', freq='M')
all_ends   = pd.date_range('2021.05.05', periods=12, freq='M')

print(all_ends)

for start, end in zip(all_starts, all_ends):
    print(start.to_pydatetime().date(), '|', end.to_pydatetime().date())

DatetimeIndex(['2021-05-01', '2021-06-01', '2021-07-01', '2021-08-01',
               '2021-09-01', '2021-10-01', '2021-11-01', '2021-12-01',
               '2022-01-01', '2022-02-01', '2022-03-01', '2022-04-01'],
              dtype='datetime64[ns]', freq='MS')

DatetimeIndex(['2021-05-31', '2021-06-30', '2021-07-31', '2021-08-31',
               '2021-09-30', '2021-10-31', '2021-11-30', '2021-12-31',
               '2022-01-31', '2022-02-28', '2022-03-31', '2022-04-30'],
              dtype='datetime64[ns]', freq='M')

2021-05-01 | 2021-05-31
2021-06-01 | 2021-06-30
2021-07-01 | 2021-07-31
2021-08-01 | 2021-08-31
2021-09-01 | 2021-09-30
2021-10-01 | 2021-10-31
2021-11-01 | 2021-11-30
2021-12-01 | 2021-12-31
2022-01-01 | 2022-01-31
2022-02-01 | 2022-02-28
2022-03-01 | 2022-03-31
2022-04-01 | 2022-04-30

EDIT:

I found out that standard module calendar can gives number of days and weeks in month.

weeks, days = calendar.monthrange(year, month)

Working example:

import calendar

year  = 2022
month = 5

for number in range(1, 13):
    if month > 1:
        month -= 1
    else:
        month = 12
        year -= 1
        
    weeks, days = calendar.monthrange(year, month)

    print(f'{number:2} | {year}.{month:02}.01 | {year}.{month:02}.{days}')

Result:

 1 | 2022.04.01 | 2022.04.30
 2 | 2022.03.01 | 2022.03.31
 3 | 2022.02.01 | 2022.02.28
 4 | 2022.01.01 | 2022.01.31
 5 | 2021.12.01 | 2021.12.31
 6 | 2021.11.01 | 2021.11.30
 7 | 2021.10.01 | 2021.10.31
 8 | 2021.09.01 | 2021.09.30
 9 | 2021.08.01 | 2021.08.31
10 | 2021.07.01 | 2021.07.31
11 | 2021.06.01 | 2021.06.30
12 | 2021.05.01 | 2021.05.31

javascript date, get past 12 months

You want to subtract 1 month only so don't use i coz it is dynamic value . The first loop is no need to subtract so do as below

Updated : you need to move current date declaration in loop , coz setMonth will change your date value so need to call current date everytime you loop...

function formatDate(date) {
    date = new Date(date);    var day = date.getDate();    var monthIndex = date.getMonth();    var year = date.getFullYear();
    return day + ' ' + monthIndex + ' ' + year;}
for ( let i=11; i>=0; i--) {    let now = new Date();    let newdate = now.setMonth(now.getMonth() - i);    console.log(formatDate(newdate ));}