Several commentators think that this verse is a late addition to the text of Daniel, so some correct it, and others transfer all (Revised English Bible) or parts (Good News Translation) of it to a footnote. As indicated in Hebrew Old Testament Text Project/Critique Textuelle de l’Ancien Testament, there are three separate textual problems in this verse alone:

(a) Are the words “and I, in the first year of Darius the Mede” a part of the original text?
(b) Did the original text have “my standing up (was),” translated I stood up (Revised Standard Version), or did it have “with me” (New English Bible and New Jerusalem Bible)?
(c) Is the pronoun at the end of the verse “for him” or “for me”?

Hebrew Old Testament Text Project recommends that: (1) the dating be retained, (2) translators render the words “my standing up” in the sense of “my intervention (took place),” and (3) the final pronoun be translated “(to strengthen) him.” It will be noted that Good News Translation does the opposite in every case, since it follows the reading of the ancient Greek version on problems (b) and (c), and makes a change in the text with regard to problem (a).

While it is impossible to make firm recommendations where the text is so jumbled, it is suggested that it may be possible to make sense of the Hebrew text as follows:
a1. Take the words “and I” as emphatic and translate them something like “I myself” or, as in Revised Standard Version, as for me ….
a2. Take the phrase in the first year of Darius the Mede as adverbial, describing the time in which the action of support or defense took place. On the dating, see comments on 6.1 and 9.1.
b. Follow the interpretation suggested by Hebrew Old Testament Text Project, so that the words “my standing up” can be translated in the sense “I supported” or “I stood firm.”
c. Translate the pronoun as “him” at the end of the verse. This may require a relative clause construction such as “whom I supported” or “whom I strengthened” in some languages. The pronoun refers, of course, to Michael, who is named in 10.21.

The resulting translation can be something like the following: “As for me, I supported and strengthened him in the first year of the rule of Darius the Mede” or “I myself helped and strengthened him during the first year when Darius the Mede was King.” Taken together with the previous verse (10.21), the rendering may come out something like “no one helps me to combat these enemies except for Michael, the guardian angel of Israel, whom I myself helped and supported during the first year of Darius, the Mede” (Bible en français courant). In some languages this will be better rendered as a separate sentence: “I myself strengthened and helped him during the first year that Darius was chief of the Medes.”

It will be noted that many English versions omit the time reference because they feel that its insertion makes very awkward style (Good News Translation, New English Bible, New American Bible, and New Jerusalem Bible). See the Good News Translation footnote on 10.20-21. On the other hand, certain versions are able to make sense of the text along the lines indicated above (New International Version and New Jerusalem Bible, as well as Revised Standard Version).

Quoted with permission from Péter-Contesse, René & Ellington, John. A Handbook on Daniel. (UBS Helps for Translators). New York: UBS, 1994. For this and other handbooks for translators see here .