Question

s = “2/29/2010”

how to validate the above string is a valid date in Lua?

Answer 1

There is no such thing in the standard Lua library, but can be easily created yourself:

function is_valid_date(str)

  -- perhaps some sanity checks to see if `str` really is a date

  local m, d, y = str:match("(%d+)/(%d+)/(%d+)")

  m, d, y = tonumber(m), tonumber(d), tonumber(y)

  if d < 0 or d > 31 or m < 0 or m > 12 or y < 0 then
    -- Cases that don't make sense
    return false
  elseif m == 4 or m == 6 or m == 9 or m == 11 then 
    -- Apr, Jun, Sep, Nov can have at most 30 days
    return d <= 30
  elseif m == 2 then
    -- Feb
    if y%400 == 0 or (y%100 ~= 0 and y%4 == 0) then
      -- if leap year, days can be at most 29
      return d <= 29
    else
      -- else 28 days is the max
      return d <= 28
    end
  else 
    -- all other months can have at most 31 days
    return d <= 31
  end

end

(untested!)

Or do a search for “lua date parsing” to find a 3^rd party library that will do this for you.