The official Easter holiday is from Friday 18th (called Good Friday) to Easter Monday, 21st.
Note: we write 18th or 5th etc but we say “the 18th” or “the 5th”.
Pronunciation: before a vowel like “eighteenth” we usually pronounce “the” with a long “e” sound e.g. “thee eighteenth”. However, many young people do not say it this way. They say “the” before a vowel exactly the same as before a consonant.
Remember: language changes and young people lead the changes.