In the absence of any other information, yes. If today is April 28th, and they are available now and will be available for the next 30 days, that should mean they will be available from April 28th through May 27th. (However, the exact beginning and ending dates in this wording can be ambiguous - it's really best to have the dates written out.)

i think the key point is that when the effective date is , if you can find some informtion about this date according to the entire context, it ill be easier to understand... hope this can help ~