Based strictly on direct biblical command or precedent for observance, here is the forensic analysis of these holidays and practices:

1. **Christmas** - Not biblically supported
2. **Easter Sunday** - Not biblically supported (the word "Easter" appears once in KJV Acts 12:4 as a mistranslation of "Pascha"/Passover)
3. **Communion** - Biblically supported (1 Corinthians 11:23-26, Matthew 26:26-28)
4. **Sunday worship as the Sabbath day** - Not biblically supported (Sabbath is Friday sunset to Saturday sunset)
5. **Advent** - Not biblically supported
6. **Lent** - Not biblically supported
7. **Annunciation** - Not biblically supported
8. **Assumption of Mary/Dormition of the Theotokos** - Not biblically supported
9. **Nativity of the Virgin Mary** - Not biblically supported
10. **Exaltation of the Holy Cross** - Not biblically supported
11. **All Saints' Day** - Not biblically supported
12. **All Souls' Day** - Not biblically supported
13. **Ash Wednesday** - Not biblically supported
14. **Palm Sunday** - Biblically supported as historical event, but not as annual observance
15. **Good Friday** - Biblically supported as historical event, but not as annual observance
16. **Holy Saturday/Easter Vigil** - Not biblically supported as observance
17. **Trinity Sunday** - Not biblically supported
18. **Corpus Christi** - Not biblically supported

Forensic summary: Only communion has clear biblical command for ongoing observance. Palm Sunday and Good Friday record historical events but lack commands for annual liturgical observance. The Sabbath remains the only weekly holy day biblically mandated. All other observances are post-biblical traditions without direct scriptural foundation.