Inconsistent UWP DateTimeFormatter output for similar patterns with en-US culture

[hemapriya-gv-17087]

I'm using Windows.Globalization.DateTimeFormatting.DateTimeFormatter in a UWP app with the culture set to "en-US". I noticed inconsistent formatting between two similar patterns.

Scenario:
Pattern: "day month.abbreviated year hour minute"
→ Output: 03-Jun-25 10:53 AM

Pattern: "day month.abbreviated hour minute"
→ Output: Jun 3 10:53 AM

Despite both using "day" and "month.abbreviated", the order of components differs depending on whether year is included or not.

Expectation:
Both formats should follow a consistent order like MM/dd/yyyy for a given culture ("en-US" in this case).

Ways to Reproduce:

string format1 = "day month.abbreviated year hour minute";
string format2 = "day month.abbreviated hour minute"
DateTimeFormatter formatter1 = new DateTimeFormatter(format1 , new[] { "en-US" });
DateTimeFormatter formatter2 = new DateTimeFormatter(format2 , new[] { "en-US" });
var output1 = formatter1.Format(DateTime.Now);
var output2 = formatter2.Format(DateTime.Now);

[Ix3WUhpgTPE]

This inconsistency seems to stem from how the DateTimeFormatter interprets the components based on the inclusion of the year. Have you checked the underlying locale-specific formatting rules defined in the Windows.Globalization.DateTimeFormatting namespace? It might be worthwhile to look into the DateTimeFormatter class documentation to see if there's a defined structure for formatting patterns involving optional elements. Additionally, can you confirm if this behavior is consistent across other cultures or just "en-US"?

[UfBt12qJNZKcw]

It seems the DateTimeFormatter is adapting the output format based on the presence of the year, which aligns with locale-specific rules. Have you tried explicitly setting the DateTimeFormatter to use a custom DateTimeFormatterLongDate or DateTimeFormatterShortDate to see if that yields more consistent results across different patterns?