Date windowing is a method by which dates with two-digit years are converted to and from dates with four-digit years.[1] The year at which the century changes is called the pivot year of the date window.[2] Date windowing was one of several techniques used to resolve the year 2000 problem in legacy computer systems.[3]
- Excel Format For Two Digit Date And Four Digit Year Mac 2018 Release
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Reasoning[edit]
For organizations and institutions with data that is only decades old, a 'date windowing' solution was considered easier and more economical than the massive conversions and testing required when converting two-digit years into four-digit years.[4][3] Iomega zip tools driver 5.01 for mac windows 7.
Using the same dates data set, we'll focus on the data in the fourth column. Here, the date is represented as a six digit string in the year, month, date format. So the date for the first entry is April 22nd 2017. Notice that it has no separating hyphens or slashes, and a year is in 2 digit format. Jan 01, 2019 Zero (0) is used to force the display of insignificant zeros when a number has fewer digits than than zeros in the format. For example, the custom format 0.00 will display zero as 0.00, 1.1 as 1.10 and.5 as 0.50. Pound sign (#) is a placeholder for optional digits. When a number has fewer digits than # symbols in the format, nothing will be displayed.
Windowing methods[edit]
There are three primary methods used to determine the date window:
- Fixed pivot year: simplest to code, works for most business dates.
- Sliding pivot year: determined by subtracting some constant from the current year, typically used for birth dates.
- Closest date: Three different interpretations (last century, this century, and next century) are compared to the current date, and the closest date is chosen from the three.
FOCUS[edit]
Information Builders's FOCUS 'Century Aware' implementation[5] allowed the user to focus on field-specific and file-specific settings.
This flexibility gave the best of all three major mechanisms: A school could have file RecentDonors set a field named BirthDate to use
- DEFCENT=19 YRTHRESH=31, covering those born 1931-2030.
Those born 2031 are not likely to be donating before 2049, by which time those born 1931 would be 118 years old, and unlikely current donors.DEFCENT and YRTHRESH for a file containing present students and recent graduates would use different values.
Examples[edit]
Unix and Windows systems have environment variables that set the fixed pivot year for the system. Any year after the pivot year will belong to this century (the 21st century), and any year before or equal to the pivot year will belong to last century (the 20th century).[6]
Some products, such as Microsoft Excel 95 used a window of years 1920–2019 which had the potential to encounter a windowing bug reoccurring only 20 years after the year 2000 problem had been addressed.[7] Video capture for macbook pro.
Below is a simple example of fixed date windowing COBOL code, often used to figure the century for ordinary business dates.
The above 'fixed-60' code establishes a fixed date window of 1960 through 2060. It assumes that none of the dates are before 1960, and should work until the year 2060.[3]
![Excel format for two digit date and four digit year mac 2018 release Excel format for two digit date and four digit year mac 2018 release](/uploads/1/2/6/6/126676919/742033806.png)
See also[edit]
- Serial number arithmetic, a form of windowing for sequential counters
References[edit]
- ^Bridis, Ted (16 March 1999). 'Temporary Y2K fix may last only a generation'. Online Athens. Archived from the original(html) on 4 March 2016. Retrieved 13 February 2020.
Using windowing, programmers instruct software to guess the century for dates that fall within a specific 'window' of time, such as the next three decades. The computer interprets the year based on a future so-called hinge date, or pivot, that programmers choose arbitrarily
- ^Healton, Gilbert (12 July 2014). 'The Best of Dates, The Worst Of Dates'. Archived from the original(html) on 13 February 2020. Retrieved 13 February 2020.
A pivot year, also known as date windowing, takes a two-digit year and expands it to determine which century the year is in. Typically the year is converted to either a full four-digit year or into the year-1900 format, as appropriate to the application at hand.
- ^ abcHoward, Raymond B. 'The Case for Windowing: Techniques That Buy 60 Years'. Year/2000 Journal (Mar/Apr 1998).
Windowing is a long-term fix that should keep legacy systems working fine until the software is redesigned and/or replatformed.
- ^McNish, Larry (30 December 2019). 'The Y2K Pivot Year Problem'. Archived from the original on 15 January 2020. Retrieved 13 February 2020.
The choice of the actual pivot year was made by companies based on their historical records. It was in no way an industry standard, nor was this approach in any way professionally recommended. But it would work for a while.
- ^Kruskopfs, Peter. 'Solving the Date Dilemma'. Information Builders. p. 4. Archived from the original on 27 December 1996. Retrieved 2 March 2020.
expanded version of the sliding windows technique . File and field level settings
- ^'Chapter 1: Pivot Year'. APPX Software, Inc. 2003. Archived from the original(html) on 22 September 2012. Retrieved 13 February 2020.
By defining a pivot year, you direct APPX to determine what century a particular year belongs to. For example, if the pivot year is set to 35, then any date field with a year greater than 35 will be assumed by APPX to have a century value of 19. Any date field with a year less than or equal to the pivot year will be assumed by APPX to have a century value of 20.
- ^Livingston, Brian (9 February 1999). 'COMPUTING Spot & fix Y2K problems in Windows 9x & NT'. CNN. Archived from the original(html) on 17 May 2001. Retrieved 13 February 2020.
The other common behavior that Windows users will experience involves dates in spreadsheet programs such as Microsoft Excel, Lotus 1-2-3, and Corel Quattro Pro. If you have typed all your dates with four-digit years (such as 1/1/1999 and 1/1/2000), you should be fine. But if you have typed two-digit years (such as 1/1/29), you may be surprised at the way different programs handle the date.
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Summary
When you type a date using a two-digit year number (such as 98), Microsoft Excel uses specific rules to determine which century to use for the date. This article explains how Microsoft Excel determines the century.
More information
When you type a date in a cell, if you omit the century digits from the year, Excel automatically determines which century to use for the date.
For example, if you type 7/5/98, Excel automatically uses the year 1998 and changes the date to 7/5/1998 in the formula bar.
The following sections explain the default rules that Excel uses.
Using the Regional Settings in Control Panel
Excel first interprets dates according to the date ordering defined by the Short date style setting under Regional Settings in Control Panel, for example, M/d/yy.
If you are running Microsoft Windows 98 or later, you can use the When a two digit year is entered, interpret a year between setting under Regional Settings in Control Panel to determine the cutoff year for the century. The default value is 2029, but you can change this to any value between 99 and 9999.
Excel Format For Two Digit Date And Four Digit Year Mac 2018 Release
Note
You can change the When a two digit year is entered, interpret a year between setting to a value that is not compatible with Excel. If you enter an incompatible value, Excel will revert to the rules discussed in the 'The 2029 Rule' section of this article.
To change the century cutoff date, follow these steps: Windows embedded posready 2009 serial key download.
- Click Start, point to Settings, and then click Control Panel.
- Double-click the Regional Settings icon.
- Click the Date tab.
- In the When a two digit year is entered, interpret a year between box, type the cutoff year that you want, and then click OK.
The following table illustrates the effect that various cutoff years will have when you type a two-digit year in Excel:
Regional Settings|Setting |Date typed |Date used||----------|------------|------||2039| 9/7/70| 9/7/1970||2039| 2/3/27| 2/3/2027||2075| 9/7/70| 9/7/2070||2099| 2/3/27| 2/3/2027|
Excel Format For Two Digit Date And Four Digit Year Mac 2018 Price
Note
Excel Format For Two Digit Date And Four Digit Year Mac 2018 Free
This will modify the way Excel interprets dates only when they are typed into a cell. If you import or programmatically enter a date, the following 2029 rule is always in effect.
The 2029 Rule
By default, Excel determines the century by using a cutoff year of 2029, which results in the following behavior:
- Dates in the inclusive range from January 1, 1900 (1/1/1900) to December 31, 9999 (12/31/9999) are valid.
- When you type a date that uses a two-digit year, Excel uses the following centuries:Two-digit|year typed| Century used||----------|----------------||00-29| 21st (year 2000)||30-99 |20th (year 1900)|For example, when you type the following dates, Excel interprets these as follows:
Date typed Date used 7/4/00 7/4/2000 1/1/10 1/1/2010 12/31/29 12/31/2029 1/1/30 1/1/1930 7/5/98 7/5/1998 12/31/99 12/31/1999 - If you want to type a date that is before January 1, 1930, or after December 31, 2029, you must type the full four-digit year. For example, to use the date July 4, 2076, type 7/4/2076.
Entering Dates That Contain Only Day/Month or Month/Year Components
So far, this article has discussed how Excel interprets three-part date entries that contain month, day, and year components. It is possible to enter a two-part date that contains only the day and month, or the month and year components of the date. Two-part dates are inherently ambiguous and should be avoided if possible. This section discusses how Excel handles date entries that contain only two parts.
When you enter a date that contains only two of the three date components, Excel assumes that the date is in the form of Day/Month or Month/Year. Excel first attempts to resolve the entry as a Day/Month entry in the current year. If it cannot resolve the entry in the Day/Month form, Excel attempts to resolve the entry in the Month/Year form, using the first day of that month. If it cannot resolve the entry in the Month/Year form, Excel interprets the entry as text.
The following table illustrates how Excel interprets various date entries that contain only two of the three date components.
Note
This table assumes that the current year is 1999.
Entry | Resolution |
---|---|
12/01 | 12/1/1999 |
12/99 | 12/1/1999 |
11/95 | 11/1/1995 |
13/99 | 13/99 (text) |
1/30 | 1/30/1999 |
1/99 | 1/1/1999 |
12/28 | 12/28/1999 |
Note
![Excel Format For Two Digit Date And Four Digit Year Mac 2018 Excel Format For Two Digit Date And Four Digit Year Mac 2018](/uploads/1/2/6/6/126676919/202650429.png)
This table illustrates how Excel stores the date, not how the date is displayed in the cell. The display format of the date varies according to the date formats that have been applied to the cell, and the current settings under Regional Settings in Control Panel.