I was just browsing on Wikipedia when I came upon this. In the article, the months are affiliated with the following demons, meaning the months in which the demon is the strongest. So here, denote the demon according to your birthday. The qualities are shown below.
Belial in January
Leviathan in February
Satan in March*
Belphegor in April
Lucifer in May*
Berith in June
Beelzebub in July
Astaroth in August
Thammuz in September
Baal in October
Asmodai in November
Moloch in December
Glossary
Belial- Lies, guilt, hostility, fornication, wealth.
Leviathan- Envy
Satan- Pride
Belphegor- Sloth
Lucifer- Pride
Berith- Murder, blasphemy
Beelzebub- destroys by means of tyrants, causes demons to be worshiped, arouses desires in priests, brings about jealousies and murders, and instigates wars.
Astaroth- inquisitors and accusers
Thammuz- Ambassador of Hell, master of big weapons
Baal- Those who invoke him makes them invisible. Make people wise, speak hoarsely.
Asmodai- Lust
Moloch- Instigates human sacrifice
For more-
Demon Names
*- Sometimes they are categorized as different or sometimes same.