Automatic brew update by Launchd Agent

com.brew.update.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key>
  <string>com.brew.update</string>
  <key>RunAtLoad</key>
  <true/>
  <key>ProgramArguments</key>
  <array>
    <string>/usr/local/bin/zsh</string>
    <string>-c</string>
    <string>/usr/local/bin/brew update</string>
  </array>
  <key>StartCalendarInterval</key>
  <dict>
    <key>Hour</key>
    <integer>10</integer>
    <key>Minute</key>
    <integer>00</integer>
  </dict>
  <key>StandardOutPath</key>
  <string>/path/to/logs/brew_update.out</string>
  <key>StandardErrorPath</key>
  <string>/path/to/logs/brew_update.err</string>
</dict>
</plist>