Help with creating a merge statement

[kaber309]

Sorry if this is a basic question, but I am new to both postgres and node.

I have the following postgres table defined:

CREATE TABLE events (
    id serial PRIMARY KEY NOT NULL,
    externalid varchar(256) NOT NULL,
    sport varchar(256) NOT NULL,
    title varchar(256) NOT NULL,
    startdate timestamp without time zone NOT NULL,
    home varchar(256) NOT NULL,
    away varchar(256) NOT NULL
)

and an array of the following type:

export interface SportEvent {
  externalid: string;
  sport: string;
  title: string;
  startdate: Date;
  home: string;
  away: string;
}

A simple insert like this works fine:
await sql`insert into events ${sql(events)}`;

But ideally I would like to perform a merge query that will insert any items that exist in the array but not in the database, and update any existing records if there is a match with an item in the array.

This is my query currently:

await sql`
MERGE INTO events AS target
USING (VALUES ${sql(events)})
  AS source(externalid, sport, title, startdate, home, away)
ON target.externalid = source.externalid
WHEN MATCHED THEN
  UPDATE SET title = source.title
WHEN NOT MATCHED THEN
  INSERT (externalid, sport, title, startdate, home, away)
  VALUES (source.externalid, source.sport, source.title, source.startdate, source.home, source.away);
`;

but this gives me the following error:
column "startdate" is of type timestamp without time zone but expression is of type text

However, if I use a specific array item like so, the merge does work:

const test = events[0];
test.title = "test123";
await sql`
MERGE INTO events AS target
USING (VALUES ${sql(events)})
  AS source(externalid, sport, title, startdate, home, away)
ON target.externalid = source.externalid
WHEN MATCHED THEN
  UPDATE SET title = source.title
WHEN NOT MATCHED THEN
  INSERT (externalid, sport, title, startdate, home, away)
  VALUES (${test.externalid}, ${test.sport}, ${test.title}, ${test.startdate}, ${test.home}, ${test.away});
`;

Given that the first and third examples I gave work, I'm inclined to think that the issue is not with the type as I have it in my application nor with the syntax of the merge, but I could be wrong. I have tried using startdate::timestamp in the VALUES clause of the merge and changing the type of startdate to be a string, along with a few other attempts, but nothing seems to work. Any help would be greatly appreciated.