You need to add these options in your hosts definitions (and services):
Where notification_interval is in minutes; notification_period is defined timeperiod; and notification_options are a comma separated list containing: w,u,c,r (w = Warning, u = Undefined, c = Critical, r = Recovery)
A timeperiod is defined like this:
# '24x7' timeperiod definition
alias 24 Hours A Day, 7 Days A Week
And you will only receive notifications within those time periods.
Hope this helps.