Convert date text into another format

any idea here like how to convert from this date format like "July 01, 2021" to appian accepted date value where we can use cal function directly?

There is no built in reverse parsing of date strings. But the following snippet should get you started.

a!localVariables(
  local!input: "July 01, 2021",
  local!monthStrings: text(eomonth(date(2020, 1, 1), enumerate(12)), "mmmm"),
  local!parts: split(local!input, " "),
  userdate(
    local!parts[3],
    lookup(local!monthStrings, local!parts[1]),
    tointeger(local!parts[2])
  )
)

I did use this kind of same logic for a E2E conversion and calculation Thanks ! Your Idea did help me with the baseline