Pivot, dynamic data source - excel

Question

I have a pivot chart which currently has the data source referring to my table.
Every week I run my code and a new row of data is appended to the bottom of my table.
The pivot does pick up this new data every week as it refers to the table, however, I want to take one less week each week So I have a years worth of data. So I want to include around rows.
Is there anyway to adjust my table to only include the years worth of rows?
Here is my sample data:
+----------+------------------+-----------------+
| week | stack | overflow |
+----------+------------------+-----------------+
| 12/20/17 | -142,335,432.00 | -41,641,109.88 |
| 12/27/17 | -105,428,220.20 | -47,448,990.63 |
| 1/3/18 | -88,520,154.56 | -24,858,774.97 |
| 1/10/18 | -42,033,431.10 | 14,573,779.35 |
| 1/17/18 | -66,101,748.16 | -8,670,735.22 |
| 1/24/18 | -75,871,649.12 | -18,000,154.21 |
| 1/31/18 | -77,027,686.63 | -11,784,198.64 |
| 2/7/18 | -96,720,126.71 | -52,219,288.98 |
| 2/14/18 | -119,118,554.60 | -34,743,350.28 |
| 2/21/18 | -116,529,554.70 | -20,774,072.93 |
| 2/28/18 | -86,871,998.53 | -25,993,521.20 |
| 3/7/18 | -90,351,387.27 | -21,259,727.05 |
| 3/14/18 | -77,968,076.28 | -51,609,924.29 |
| 3/21/18 | -120,805,352.60 | -40,338,490.97 |
| 3/28/18 | -92,247,583.62 | -14,525,648.04 |
| 4/4/18 | -70,821,451.36 | -35,866,864.46 |
| 4/11/18 | -82,694,486.66 | -59,009,729.82 |
| 4/18/18 | -79,034,094.39 | -64,231,312.42 |
| 4/25/18 | -63,415,815.16 | -28,612,265.37 |
| 5/2/18 | -80,372,191.96 | -53,375,611.61 |
| 5/9/18 | -72,619,415.73 | -50,642,469.19 |
| 5/16/18 | -109,654,240.70 | -45,762,784.43 |
| 5/23/18 | -100,407,366.50 | -39,577,966.11 |
| 5/30/18 | -105,794,095.80 | -65,071,199.59 |
| 6/6/18 | -83,630,201.98 | -60,981,969.88 |
| 6/13/18 | -104,644,821.50 | -63,754,760.71 |
| 6/20/18 | -75,229,424.33 | -55,803,681.24 |
| 6/27/18 | -65,237,135.62 | -54,693,832.65 |
| 7/4/18 | -60,025,672.33 | -44,367,918.60 |
| 7/11/18 | -30,172,175.09 | -28,392,163.28 |
| 7/18/18 | -20,687,864.39 | 24,300,285.63 |
| 7/25/18 | -40,476,447.03 | 4,850,881.09 |
| 8/1/18 | -31,211,625.05 | -67,887,918.30 |
| 8/8/18 | -29,736,938.87 | -32,905,703.80 |
| 8/15/18 | -74,934,647.91 | -65,611,884.73 |
| 8/22/18 | -25,220,747.20 | -7,019,746.86 |
| 8/29/18 | -24,608,552.13 | -8,065,633.97 |
| 9/5/18 | -30,119,599.95 | -26,225,633.08 |
| 9/12/18 | -29,836,379.12 | -10,045,560.95 |
| 9/19/18 | -61,281,567.61 | -58,427,878.27 |
| 9/26/18 | -47,418,209.59 | -33,451,409.22 |
| 10/3/18 | -41,321,336.46 | -25,112,764.44 |
| 10/10/18 | -1,241,932.51 | 21,814,274.35 |
| 10/17/18 | -19,791,273.66 | -12,199,449.75 |
| 10/24/18 | -20,501,406.84 | 1,225,387.11 |
| 10/31/18 | -64,116,464.30 | -5,308,628.21 |
| 11/7/18 | -83,657,672.02 | -19,922,992.91 |
| 11/14/18 | -112,704,007.53 | -32,939,535.69 |
| 11/21/18 | -71,969,954.54 | -51,335,709.79 |
| 11/28/18 | -79,668,484.56 | -67,887,918.30 |
| 12/5/18 | -44,134,343.99 | -32,905,703.80 |
| 12/12/18 | -71,700,079.84 | -65,611,884.73 |
| 12/19/18 | -82,238,011.30 | -74,725,620.20 |
| 12/26/18 | -59,385,932.41 | -54,947,256.94 |
| 1/2/19 | -42,717,830.26 | -31,110,199.14 |
| 1/9/19 | -11,029,444.63 | 7,309,440.90 |
+----------+------------------+-----------------+

Answer 1

Changing the source range for the pivot will be tricky as Excel does not allow non-contiguous cells to be used in pivot tables. Instead you can create the pivot by selecting entire column to account for all future entries.
Then the pivot can be manipulated to show a changing range as shown in the code below.
Hope that works for you.
EDIT
The code is updated below to include 50(can be changed) from the bottom.
Sub MovingPivot()
Dim ws As Worksheet
Dim dtTop As Date
Dim i As Integer, n As Long
Const NumWeeks = 50 'Change this to set weeks range
Set ws = ActiveSheet 'Set reference to your worksheet here
'reset the pivot filters
ws.PivotTables("Table1").PivotFields("Date").ClearAllFilters
'remove blank values
ws.PivotTables("Table1").PivotFields("Date").PivotItems("(blank)").Visible = False
'find the date entry in 50 places from bottom.
i = 0
For n = ws.PivotTables("Table1").RowRange.Count To 1 Step -1
If i = NumWeeks Then
dtTop = ws.PivotTables("Table1").RowRange.Cells(n).Value
Exit For
End If
i = i + 1
Next n
ws.PivotTables("Table1").PivotFields("Date").PivotFilters.Add2 Type:=xlAfterOrEqualTo, Value1:=Format(dtTop, "dd-mmm-yyyy")
End Sub

Answer 2

If you want to continue using a Pivot Chart, you can use the time line slicer to include/exclude data. You'll need to adjust the time line or filter manually after the data has refreshed. Or write VBA to set the filters.
A non-vba version that does not require slicers can also be achieved with a standard chart (not a pivot chart). Create named ranges with Offset functions that grab just the rows of data that you are interested in, then plug these range names into the standard chart. When new data is added to the table, the named ranges that feed the standard chart will also be updated.
If you need a step by step, take a look at https://peltiertech.com/Excel/Charts/DynamicLast12.html