centenary

at fixed intervals

done or occurring every hour

at fixed intervals

done, happening etc once a month; valid for one month

at fixed intervals

now and then; sometimes

every now and then

of, concerning, an orbit; a circular motorway round a city (e.g. the London Orbital)

at fixed intervals

occurring or appearing at regular intervals

at fixed intervals

occasionally; from time to time

every now and then

intermittently

intermittently