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Pack julian_lang_en -- prolog/julian/lang/en.pl
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Parse an English language date or time phrase into a library(julian) form. One usually interacts with library(julian/lang/en) by calling Julian's form_time/2 predicate using the english/1 form. For example, form_time(english("tuesday or thursday in April"), Dt). However, it's sometimes convenient to separate the parsing and constraining steps. In that case, call english_form//1 directly:
?- phrase(english_form(Form), "tuesday or thursday in April").
Form = [month(april), dow([tuesday, thursday])].

This predicate is declared multifile so that you can add additional English phrases to suit your needs. Perhaps defining what "summer" means to you:

julian_lang_en:english_form(month([june,july,august])) -->