Simple thinking kuriakê is Sunday or 1st day in Greek.

The wording " - tê kuriakê hêmera " has been used since the 2nd century that reffers to Sunday.

"Lord's Day" is the English translation of the ancient Greek kyriake hemera, a term that first appears in Christian literature in the latter half of the first century. Within a few decades, however, the term kyriake hemera became ubiquitous in Christianity, so that hemera was ellided. Thus, when a Christian writer referred to the kyriake, his readers understood that Sunday was meant.

The first appearance of the term kyriake hemera is in the New Testament, in the Book of Revelation, which was written in the latter decades of the first century. In Rev. 1:10, the author writes, "I was in the Spirit on the Lord's Day." Most Christian commentators interpret Rev. 1:10 as a reference to Sunday, but some argue that because Revelation contains numerous eschatological visions, kyriake hemera in this passage should be taken as a reference to the end of the world or Judgment Day, which Old Testament prophets often called the Day of the Lord. However, in the Septuagint, the Greek translation of the Old Testament, as well as in the original Greek texts of the New Testament, the eschatological judgment day is called hemera tou kyriou, never kyriake hemera. It is possible that when Christians began to call Sunday "the Lord's Day," they opted for kyriake hemera because hemera tou kyriou already had acquired its own connotation or meaning due to the Septuagint rendering.

Some seventh-day Sabbatarian writers have argued that because Jesus identified himself as "Lord even of the Sabbath day" (cf. Matt. 12:8), kyriake hemera in Rev. 1:10 should be interpreted as a reference to seventh-day Sabbath. However, in almost every other instance where kyriake hemera or kyriake is used, the unambiguous meaning is Sunday, but there are no early witnesses to the use of kyriake hemera as a name for Saturday.

I can't remember what Samuel Bacchiocchi said about this (i.e. the "Lord's day"). Anyone know?

The claim that "the book of Revelation gives evidence of calling the first day of the week 'the Lord's Day' (Rev 1:10)" (#21), cannot be supported by the usage of the phrase in the NT or contemporary literature.

The first clear designation of Sunday as "Lord's day" occurs toward the end of the second century in the apocryphal Gospel of Peter. This usage cannot be legitimately read back into Revelation 1:10. A major reason is that if Sunday had already received the new appellation "Lord's day" by the end of the first century, when both the Gospel of John and the book of Revelation were written, we would expect this new name for Sunday to be used consistently in both works, especially since they were apparently produced by the same author at approximately the same time and in the same geographical area.

If the new designation "Lord's day" already existed by the end of the first century, and expressed the meaning and nature of Christian Sunday worship, John would hardly have had reasons to use the Jewish phrase "first day of the week" in his Gospel.

Therefore, the fact that the expression "Lord's day" occurs in John's apocalyptic book but not in his Gospel-where the first day is explicitly mentioned in conjunction with the resurrection (John 20:1) and the appearances of Jesus (John 20:19, 26)-suggests that the "Lord's day" of Revelation 1:10 can hardly refer to Sunday. (For a discussion of this text, see my dissertation From Sabbath to Sunday, pp. 111-131).

According to my Strong's greek, kuriakos means belonging to the Lord and hemera can mean gentle, day and can include parts of other days, period of time, for ever, judgement, while, years.

I'd be interested in how it would mean Sunday.

In reading the verse, I could see how alternatives could be:
I was in the Spirit on the day of the flood.
I was in the Spirit at creation.
I was in the Spirit in the future.
I was in the Spirit on the day of the Lord.

I would therefore, tend to agree with Will, and that this verse is setting the setting of what is to follow.