Timestamp Microservice 'franzu'

Code Feedback
1

I finished my project and the results seems good, but if someone can tell me something wrong about the thinking-process, method used or something else, I would really appreciate.

ISO-8601 format:
https://violet-timestamp.glitch.me/api/timestamp/2010-6-2

Timestamp format:
https://violet-timestamp.glitch.me/api/timestamp/323434827484

Now:
https://violet-timestamp.glitch.me/api/timestamp/

The code:

app.get("/api/timestamp/:date_string?", function(req, res){
  
  let apiDate = req.params.date_string;
  
// if params === undefined throw new Date

  if(apiDate === undefined){
    
    let time = new Date();
    
    res.send({unix: time.getTime(), utc: time.toUTCString()});
    
  }
  
//check if there's a dash for the ISO-8601 format 
//and parse the date, else perform a conversion from timestamp

  if(apiDate.indexOf('-') !== -1){
    
    let parsing = Date.parse(apiDate);
    let utcDate = (new Date(parsing)).toUTCString();
    
    res.send({unix: parsing, utc: utcDate});
    
  } else {
    
    let utcDate = (new Date(+apiDate)).toUTCString();
    
    res.send({unix: +apiDate, utc: utcDate});
  }  
});
2

in the last else case why did u add + before apiDate