EasyPrompt, don't you think God works in sevens? 3 1/2 years + 3 1/2 years = 7 years. 2300 evening-mornings is not equal to 3 1/2 years, no matter how you work it out. Take also as an example the period mentioned at Daniel 12:11, 12. 1290 day + 1335 days = 2625 days. I view it as follows:
Daniel (7:24, 25[1]; 12:7[2]) mentions “a time, times and half a time.” Revelation (11:2, 3; 12:6, 14[3]) breaks it up into different modes of time: Time, times and half a time = 3½ years = 42 months = 1,260 days. From there, 7 years = 84 months = 2,520 days (cf. 4:25). Thus, 1 year = 360 days. All the days, times and weeks found in the books of Daniel and Revelation are connected to a half or full Heptad. Time, times and half a time = Half a Heptad. This means unfinished business (cf. Dan. 9:27; Rev. 11:11).[4]
“Go through the city, through Jerusalem, and put a mark on the foreheads of the men who are sighing and groaning over all the detestable things that are being done in the city."
Don't think you should apply this to the great tribulation as above sentence indicates.
[1] Aramaic year:) עִדָּןJArm., Syr., Heb. (מוֹעֵד Da 725, Sept. ἔτο῍ Da 416.32.34, Josephus Antiquities xii 7: 6 :: Vulgate tempus/tempora, so also Sept. καιρό῍καιροί 725 127; שִׁבְעָה עִדָּנִין Da 413.20.22.29, וּפְלַג עִדָּן עַד עִדָּן וְעִדָּנִין 725 meaning three and a half years (Bentzen 34, 67; Plöger KAT xviii: 105; see also 115f, 143). † See HALOT.
[2] Hebrew year: מוֹעֵד: מֹעֲדִיםוָחֵצִילְם׳ a time, times and a half Da 127 )as BArm. עִדָּן 2, meaning a year(. See HALOT.
[3] The expr. καιρὸν καὶ καιροὺς κ. ἥμισυ καιροῦ also belongs to the eschatol. vocab.; it means the apocalyptic time of 1 + 2 + ½ = 3½ years. See BDAG. καιρόν καί καιρούς καί ἥμισυ καιροῦ, a year and two years and six months (A. V. a time, and times, and half a time; cf. Winer’s Grammar, sec. 27, 4), Rev. 12:14 (cf. 6; from Dan. 7:25; 12:7). See Thayer.
[4] Gabriele Boccaccini, in the article “The Solar Calendars of Daniel and Enoch,” suggests that the writer of Daniel used a solar calendar, consisting of a thirty-day month x 12 = 360 day year + 4 intercalary times (i.e., the equinoxes and solstices) that were added between seasons but not counted in the reckoning of the days of the year. See The Book of Daniel: Composition and Reception. Volume 2. Edited by J. J. Collins and P. W. Flint, Brill, 2001, pp. 312-328.