Proper regular expression to find datetime in spanish

I am trying to write a regex to find a date in spanish de format is:

blabla4 de diciembre de 2018blabla

So I know I need to look for:

• 1 or 2 digits (in case date has two)
• blank space
• exact characters 'de'
• blank space
• 1 to * characters between a-z
• blank space
• excact characters 'de'
• blank space
• exactly 4 digits

re.search("\d{1,2} de [a-z]+ de \d{4}")

What am I missing?

Examples:

• mauricio2 de abril de 2016
• belice12 de enero de 2018
• australia1 de septiembre de 2015