Using Index/Match produces duplicate entries

I have a workbook with many spreadsheets, each sheet representing data for a group of equipment types. Data is entered onto the "Main Page" including a sample code that links the entry to one of the spreadsheets. The data from Main Page is captured by the linked group spreadsheet and listed in order in which it is entered (same row at it appears on Main Page). The data consists of the date and the colony count. Once the data is captured onto the spreadsheet, it is sorted by earliest date to most recent date. The corresponding colony count is listed in the column beside the sorted date.
Problem: If multiple entries are made on the same date but refer to different colony counts and different items within the same equipment group, the sorted data lists the first entry multiple times for all entries on that date.I have created a very edited version of this workbook containing 40 rows and manipulated data to have as many duplicates as possible to highlight the problem.

I tried the formulas as you suggested but got blank cells as a result. See attached. I looked up the function Aggregate in Excel Help and it was not listed. I have Excel 2007.
I even tried the array step with CTRL+Shift+Enter. Either way resulted in blank cells.

Exactly what I wanted. See your results. I played around with entries on Main Page and the data was captured exactly as it should. I will probably spend the rest of the month trying to understand the syntax and how each function contributes to the result.

One aspect of each spreadsheet that I neglected to include in the example is that 2-years of data are included on the same spreadsheet. The first set of columns is data from last year (in this case 2016). This set of data is used to establish alert and action levels using mean and std. dev. There is a second set of columns that represent the current year. Here when data is entered on the Main Page for the current year the alert/action levels are constantly being recalculated upon each entry. The results at the end of the year provide values for the next year and the cycle repeats. The date is changed from , for example, 2016 to 2017, and 2017 is changed to 2018.
The formulas you provided do not differentiate the sample date. So I have 2 sets of the same data. I have a phrase from the old sheet that selected the data based upon the date in the top of the column, but I do not know how to insert it, if at all.
Here is the phrase: (IF(YEAR('Main Page'!B$3:B$5000)=$I$3,B$11:B$5000),C11. Remember the cell references are from the actual workbook, but the principle is the same. Look at the example I sent on cell H16. That would replace I3 in the formula I printed.
I could use your expertise to resolve this issue as I am still a bit unfamiliar with the syntax and do not know how to edit it without a complete disaster.
As a reference the original Main Page has approximately 2000 rows and many more columns that provide us with information not pertinent to this issue.
C11 represents E11
B3:B5000 represent the sample date
I3 represents the year

Thank you

Vince Tentarelli

I added your formulas to the cells you recommended and the distinction for the year did indeed work. In order to make it work, however, I had to add 2 new columns for the 2017 side of the spreadsheet. I was able to remove the column with the consecutive numbers and had the 2017 data rely on the 2016 column of consecutive numbers. However, I noticed a bit of a glitch. Notice columns F & P, the sorted dates. There are dates out of order. In column P 3/2/2017 appears after 4/18/2017 & 4/20/2017. There are several examples of this sorting error. I am wondering if I did something wrong, but it must handle the possibility of entering the data out of order. That is the purpose of the Sorted Data columns.
Because this is a table, we might be able to sort the data, but some columns are not part of the data, and cell references may become corrupt. Your thoughts?
I have some questions just for my own clarification. In Column C the function ISNUMBER appears in the formula for the date. Why ISNUMBER?
What is the purpose of subtracting 10 after the ROW function? Is it to return to Row 1?

I am still amazed how quickly you responded and how elegant your solutions are. I would probably have several nested IF statements that would take up an entire page.

Vince Tentarelli

That seems the easiest and most versatile solution. That way we can sort by any category on the main page and get an instant view of any trends without complicated formulas.
Thank you for your help.