Schedule checkbox to check/uncheck background automatically

Below script was working fine yesterday, and today I have got an error:

Exception: This script has too many triggers. Triggers must be deleted from the script before more can be added.

function chEcked() {
  SpreadsheetApp.getActive().getSheetByName('To-do').getRange("F1").setValue(true);
  SpreadsheetApp.getActive().getSheetByName('OverDate').getRange("F1").setValue(true);
}

function unchEcked() {
  SpreadsheetApp.getActive().getSheetByName('To-do').getRange("F1").setValue(false);
  SpreadsheetApp.getActive().getSheetByName('OverDate').getRange("F1").setValue(true);
}

ScriptApp.newTrigger("unchEcked").timeBased().atHour(23).nearMinute(50).everyDays(1).create();

ScriptApp.newTrigger("chEcked").timeBased().atHour(18).nearMinute(50).everyDays(1).create();

What I want to do is have this script run every day at a specific time.
I know if I delete the old trigger, the script will execute successfully, but I can’t do it manually every day.
Would you modify the script to meet my need?