new_time.rb

def new_time(timestamp, options)                                                                                                                                 
  Time.new(                                                                                                                                                           
    options[:year]  || timestamp.year,                                                                                                                                
    options[:month] || timestamp.month,                                                                                                                               
    options[:day]   || timestamp.day,                                                                                                                                 
    options[:hour]  || timestamp.hour,                                                                                                                                
    options[:min]   || (options[:hour] ? 0 : timestamp.min),                                                                                                          
    options[:sec]   || ((options[:hour] || options[:min]) ? 0 : timestamp.sec),                                                                                       
    timestamp.gmt_offset                                                                                                                                              
  )                                                                                                                                                                   
end