Yesterbox for Gmail (Google Apps Script)

yesterbox.js

function yesterbox() {
  var yesterboxName = "Yesterbox";
  var backlogName = "Backlog";
  var cutoffHour = 7; // 7am each day
  var backlogCutoffDays = 10; // Older than 10 days

  var yesterboxLabel = GmailApp.getUserLabelByName(yesterboxName) || GmailApp.createLabel(yesterboxName);
  var backlogLabel = GmailApp.getUserLabelByName(backlogName) || GmailApp.createLabel(backlogName);

  var yesterboxCutoff = new Date();
  var backlogCutoff = new Date();

  yesterboxCutoff.setHours(cutoffHour, 0, 0, 0);
  backlogCutoff.setHours(cutoffHour, 0, 0, 0);
  backlogCutoff.setDate(backlogCutoff.getDate() - backlogCutoffDays);

  var yesterboxThreads = GmailApp.getInboxThreads().filter(function(thread) {
    return (thread.getLastMessageDate() < yesterboxCutoff && thread.getLastMessageDate() >= backlogCutoff);
  });

  var backlogThreads = GmailApp.getInboxThreads().filter(function(thread) {
    return (thread.getLastMessageDate() < backlogCutoff);
  });

  var completedYesterboxThreads = yesterboxLabel.getThreads().filter(function(thread) {
    return !thread.isInInbox();
  });

  var completedBacklogThreads = backlogLabel.getThreads().filter(function(thread) {
    return !thread.isInInbox();
  });

  yesterboxLabel.addToThreads(yesterboxThreads);
  yesterboxLabel.removeFromThreads(backlogThreads);
  yesterboxLabel.removeFromThreads(completedYesterboxThreads);

  backlogLabel.addToThreads(backlogThreads);
  backlogLabel.removeFromThreads(yesterboxThreads);
  backlogLabel.removeFromThreads(completedBacklogThreads);
}