Ordinals in straight Liquid templates.

liquid_ordinals.liquid

{% assign d = time | date: "%d" | plus:0 %}
{% assign d_mod = d | modulo:10 %}
{% assign ordinals = "th,st,nd,rd,th,th,th,th,th,th" | split:"," %}

{% if d > 10 and d < 14 %}
	{{ d }}th
{% else %}
	{{ ordinals[d_mod] }}
{% endif %}