Certainly.
As usual with Node-RED (and programming in general), there are various ways. However, to cover such a wide time period is probably easiest to achieve using a function node rather than a change node.
That is because you will want to:
- Capture the current date
- Generate an array of the last 18m dates
- Loop through the array and for each entry send a msg that goes to the request node
Here is something that may help with the date calculations: Subtract days from a date in JavaScript - Stack Overflow
