In Slovakian calendar (see this), on 20 Jan 2018 we could celebrate either and only one from the following:

1. Feria
2. Optional Memorial of St Fabian
3. Optional Memorial of St Sebastian
4. Votive Holy Mass in Honour to the Blessed Virgin Mary (literally translated as Optional Memorial of Virgin Mary on Saturday, for we in Slovakia have on every ferial Saturday this Optional Memorial).

This problem is with the string on the 78 line of src/locales/en.mjs, because it combine the two Optional Memorial of Sts Fabian and Sebastian into one.

Please consider to separate them for Slovakian calendar.