Query for multiple date ranges on a date field

I’m able to successfully query a date field for a date range using this syntax:

{% set entries = entries.startsOn(['and', '>= '~firstDay, '< '~ lastDay]) %}

What I would like to do however is query that field for multiple date ranges at once with an or operator.

I can do this with other fields but the date range already using an and operator complicates matters so I can’t do the same.

{% set data = data|merge(['or']) %}
{% for item in items %}
     {% set data = data|merge(['*'~item~'*']) %}
{% endfor %}

Any suggestions gratefully received!

{% set firstRange = craft.entries({fieldHandle: ['and', '>= '~date1FirstDay, '< '~ date1LastDay]}) %}
{% set secondRange = craft.entries({fieldHandle: ['and', '>= '~date2FirstDay, '< '~ date2LastDay]}) %}

{% set entries = firstRange |merge(secondRange) %}