I've made a minor study of this during the past few months, after getting burned on util, esp. by HSBC. The Amex reporting date is actually the last business day of each month, but they report the statement balance from whenever your statement closes (in my case, between the 19-21st).
Orchard reports the last business day of the month, BUT you have to pay it down the morning BEFORE that date. This reporting date is irrespective of the actual closing date (mine is the 4th and 8th, respectively).
However, HSBC reports the closing balance from the statement date for former Direct Merchants Bank MC, and doesn't follow the Orchard formula (yet).
USBank (for me, Harley-Davidson Visa) follows the same formula as Orchard - reports the balance as it stands the last business day of the month, but you have to pay it down the day before that. In my case, too, I got a CLI on the statement date, but it didn't reflect on my report till the next month. (Double burn)
Cap1 reports the statement closing balance, which is also the due date (except for last month, when they adjusted it out five days, really screwing up my util because I didn't ask about the closing date. I Assumed.)
Merrick Bank and Hooters also reports the balance the last business day of the month, and pay it the day before for it to count. Merrick also can hold the available funds unless you call them to verify with the bank that the payment cleared. Some banks won't do this in the 800-call center, but your branch probably will on a conference call.
WAMU has a very short due date to closing date cycle, usually two to three days max, but they report right away.
State Farm Visa, for me closes on the 26th each month, but for the payment to count, you have to phone it in. Web payments may post later.
Citi is wonderful. They tell you the closing date on the statement, and the time by which the payment must be made.
Juniper is screwy. If you make two payments in the month, the second will probably be posted but the funds held for up to 10 days unless you pay by Western Union, a handy thing if you really need the balance down but may need the $$ soon thereafter.
USAA reports the statement balance a day or two afterwards, but you need to check when the statement closes and be sure to pay it at least the day before.
That's what I've learned so far, at times at some cost to my score. I keep a calendar now of due dates, pay-by dates and closing dates. Cap 1 kept me from a really low util this month. Phbbt.