Javascript get timestamp of 1 month ago [duplicate]

A simplistic answer is:

// Get a date object for the current time
var d = new Date();

// Set it to one month ago
d.setMonth(d.getMonth() - 1);

// Zero the time component
d.setHours(0, 0, 0, 0);

// Get the time value in milliseconds and convert to seconds
console.log(d/1000|0);

Note that if you subtract one month from 31 July you get 31 June, which will be converted to 1 July. similarly, 31 March will go to 31 February which will convert to 2 or 3 March depending on whether it’s in a leap year or not.

So you need to check the month:

var d = new Date();
var m = d.getMonth();
d.setMonth(d.getMonth() - 1);

// If still in same month, set date to last day of 
// previous month
if (d.getMonth() == m) d.setDate(0);
d.setHours(0, 0, 0, 0);

// Get the time value in milliseconds and convert to seconds
console.log(d / 1000 | 0);

Note that JavaScript time values are in milliseconds since 1970-01-01T00:00:00Z, whereas UNIX time values are in seconds since the same epoch, hence the division by 1000.