google_sheet_reminder.js

function send_schedule_email_reminder() {
  // This first part of reading the contents can be abbrieviated probably

  var startHeaderRow = 3;
  var lastColumn = 12;
  var startContentRow = 4;
  var sheet = SpreadsheetApp.getActiveSheet();

  var header = sheet.getRange(startHeaderRow, 1, 1, lastColumn).getValues();
  // Read in header based on startHeaderRow, lastColumn
  //Ref: https://developers.google.com/apps-script/reference/spreadsheet/sheet#getRange(Integer,Integer,Integer,Integer)

  var numRows = sheet.getDataRange().getNumRows(); // Get total number rows
  var dataRange = sheet.getRange(startContentRow, 1, numRows, lastColumn);
  var data = dataRange.getValues();

  var emailAddress = "your_email_address@domain.com";
  var emailSubject = "Name_your_email_subject";
  var emailContent = "Add_introduction_text_in_email";

  var currentDate = new Date(); // Get current date
  var selectedRow;
  // Loop through the sheet for date within the next 7 days
  for (var l in data) {
    var row = data[l];
    selectedRow = row;
    var dateSchedule = row[0];
    Logger.log(dateSchedule);
    var differenceInMillis = currentDate.getTime() - dateSchedule.getTime();
    var daysDiff = Math.floor(differenceInMillis / 1000 / 60 / 60 / 24);
    if ((daysDiff <= 0) && (daysDiff >= -7)) {
      break;
    }
  }

  emailSubject += selectedRow[0].toDateString(); // Add date to subject

  // Add each column in the selectedRow of this found date, i.e., collect all fields
  emailContent += selectedRow[0].toDateString() + "\n\n"; // Add date to content

  // Collect all fields in var content
  var content = "\t";
  for (var i = 1; i < 11; i++) {
    content += header[0][i] + ": " + selectedRow[i] + "\n\t";
  }

  emailContent += content;
  emailContent += "Add_last_paragraph_of_the_email. You can also insert the hyperlink of the shared google sheet document.";

  MailApp.sendEmail(emailAddress, emailSubject,
    emailContent, {
      cc: "your_friends@domain.com"
    });
  //cc is an option: string with comman seperated email addresses
}