After a bunch of trial and error, I got the following:

Good {% assign hour = 'now' | date:'%k' | plus: -4 %} {% if hour < 12 %} morning {% elsif hour < 16 %} afternoon {% else %} evening {% endif %} {{ticket.requester.first_name}},

Here's how I understand the markup:

{% assign hour = 'now' | date:'%k' | plus: -4 %}

converts the word "hour" into a number. That number is the current hour, based on a 24 hour clock:

'now' will pull up the time when used before "| date:"

Adding " '%k' " will make it only show the hour

Adding "| plus: -4 " will subtract 4 hours from the previous number. This is because my time zone is GMT -4.

(As Graeme Carmichael wrote:

"This is the hour of day {{hour}}"

Put {{hour}} in under your code to see the number that shows up.)

At this point it's a simple if statement.

{% if hour < 12 %} morning {% elsif hour < 16 %} afternoon {% else %} evening {% endif %}