Shortcode Question/Knowledge transers

I thought I could use shortcode basically to store code/html I use a lot in a central location and link that code to a page via shortcode.

I am by no means a programmer. I learn as I go to accomplish my goals. My issue is I have created a shortcode to a section of my site that is often used (html) but when i create the code and save I receive an error "syntax error, unexpected T_STRING". It looks like the word today's is causing the issue.

How do i encapsulate all my html so that when the .php file ignores the text but runs the function.

Example below:
//Todays Timing
function TodaysTimingShortcode() {
return '<h1>Todays Timing Sheet</h1>

Use today's Shake Day timing sheet to track your success.';
add_shortcode('TodaysTiming', 'TodaysTimingShortcode');