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awkで時間をシフトして，任意の時間形式で出力(strftime)．

BEGIN{
#Shift time
#2009-07-18 12:23:38
 a = 5 #5 hours shift
}
{
 gsub(/-/," ",$1)
 gsub(/:/," ",$2)
 str=$1" "$2
#raw time 
t = mktime(str)
#shift time
t2 = mktime(str)-(60*60*5)
 
#remove 00:00:00
 str_0 = strftime("%H:%M:%S",t)
 if(str_0=="00:00:00"){
	#print str_0
	next;
 }

 #print "*"strftime("%Y/%m/%d %H:%M:%S",t)
 #str_t2 = strftime("%Y-%m-%d %H:%M:%S",t2)

#shift time output
 str_t3 = strftime("%Y-%m-%d",t2)
 x[str_t3]++;