MDC Brooklyn Handbook page 36, point 4 states he shall be given access to regular showers. Barring security concerns (eg Solitary, or low staffing) that would mean at least 1x a day. However in practice inmates can be restricted to 1x a week before any 8th Amendment “cruel and unusual punishment” concerns start cropping up. So to answer your shitty ask, 31 days in the months that have 31 days.