expression: <leftop: term termop term>
termop: 'and' | 'or' | 'xor'
term: '(' expression ')' | condition
condition: field comparison value
field: '<' timethingy '>'
timethingy: 'DAY' | 'WEEK'
comparison: '<=' | '<' | '=' | '>=' | '>' | '!='
value: /\d+/