Would ἡμέρα being in the context of ἀνακρίνω have been enough to prompt readers that it meant tribunal here? Are there other examples that establish "tribunal" as one if the ordinary meanings of ἡμέρα that language users of that period could easily choose from according to context?1 Corinthians 4:3 wrote:Ἐμοὶ δὲ εἰς ἐλάχιστόν ἐστιν ἵνα ὑφ’ ὑμῶν ἀνακριθῶ, ἢ ὑπὸ ἀνθρωπίνης ἡμέρας· ἀλλ’ οὐδὲ ἐμαυτὸν ἀνακρίνω.
BDAG page 438, column 1, states that this sense in First Corinthians is based on the Christian / Jewish usage of "the Day of the Lord" being a day of judgement.LSJ wrote:5. a fixed day, τακτὴ ἡ. Act.Ap.12.21; ῥητὴ ἡ. Luc.Alex.19; “ἡ. ἔστησαν ἀρχαιρεσιῶν” D.H.6.48, cf. Act.Ap.17.31; “ἡ. Κυρίου” LXXJl.2.1, cf. 2 Ep.Pet.3.12, etc.; “ἡ. κρίσεως” Ev.Matt.10.15: so abs., ὑπὸ ἀνθρωπίνης ἡμέρας a human tribunal, 1 Ep.Cor.4.3; “ἡμέραι καὶ ἀγῶνες” Jahresh.23Beibl.93 (Pamphyl.).
Explication of the purpose of the question.
If the purpose of the question doesn't seem clear, let me explicate a little. There is a difference between arriving at a meaning from context, and recognising which out of a range of meanings understood in a context. Context is often bandied about as the way to decide meaning for us as language users with improperly formed understandings of the language and who read with only partial recignition of the range of meanings of words, but except in a very few cases of novelty, the way that context works for a fully-formed speaker of a language is that it determines which of a range of known meanings is to be invoked.
(A) In the case that "tribunal" is an established meaning in Greek, we could consider a fundamental difference between the way that we as partially formed users of the language differ in our use of context from well-formed users of the language...
That is to say, we learners of Greek following a line like LSJ presents, might start with the meaning "day", recognise that it is a "fixed day", further recognise that the fixed day could be a "day of judgement" then go on to to conclude that it is the "process of judgement" that takes place on the fixed day, ie the "tribunal" is the intended meaning. Alternatively, following BDAG, knowing that the eschatological Great Day is a day of judgement and the most important thing on the day is the judgement, the meaning of the day is judgement, ie a "tribunal". If a well-formed speaker of a language, on the other hand, had "tribunal" as one of the established meanings of ἡμέρα, they would choose between a range of meanings for ἡμέρα based on context, one of them being "tribunal".
(B) In the case that it is novelty on Paul's part, and ie not a meaning that well-formed speakers of the language would recognise, the familiar expression the Day of the Lord is (here being tongue in cheek) parodied / trivialised to into the Day of Humans. Like being as if he might have said in English, "(Speaking in confident tones) I live my life in fear of that coming Great and Terrible Day of the Judgement of the L.. (speaking incredulously) ?!?humans?!?, (Is this for real?), NOT".
In deciding whether it was confronting comic novelty on Paul's part, or a regular meaning that he expected his listeners to be familiar with, let me ask whether there is sufficient or (even) any extant evidence of ἡμέρα being used of "tribunal" in Greek (at Corinth or more widely), in Latin or as a loan word within one of the languages of the Jewish community to establish it as a regular meaning?