Added info how to copy files without changing the timestamps

beamtime/readme.md

@@ -167,14 +167,14 @@ Beamtime data are processed in *two main phases*:
 
 ### 🔁 Typical Processing Chain
  `````
-beamtime raw files

-↓
importData.m → FileList.mat

-↓
generateSpectra.m → SpectrumList.mat

-↓
AnalysisStep4SurfaceConcentration.m → AnalysisStep4SurfaceConcentration.mat

-↓
GaussFitHClOnIce.m → GaussFitHClOnIce.mat

+beamtime raw files
+↓importData.m → FileList.mat
+↓generateSpectra.m → SpectrumList.mat
+↓AnalysisStep4SurfaceConcentration.m → AnalysisStep4SurfaceConcentration.mat
+↓GaussFitHClOnIce.m → GaussFitHClOnIce.mat
 
 SpectrumList.mat
-↓
FigureHexylamineN1sLjIce.m → FigureHexylamineN1sLjIce.mat
+↓FigureHexylamineN1sLjIce.m → FigureHexylamineN1sLjIce.mat
 ``````
 
 Reuse `.mat` outputs to skip re-running previous steps  🧠💤
@@ -258,7 +258,60 @@ save('FileList.mat',"FileList");
 - Scripts: descriptive names like `generateSpectra.m`, `PlottingForAnand.m`.
 - Output: typically script‑matching names, saved into `.mat` files.
 
-***
+### Data files date and time
+
+Copying files while preserving their original timestamps (Creation Date and Last Modification Date) is a common challenge because standard "drag-and-drop" operations often treat the copy as a "new" file created at the moment of the transfer.
+
+To do this safely and reliably, you need to use specific commands or utilities designed for archival integrity.
+
+#### 🪟 Windows 11: Using Robocopy
+
+The most robust tool built into Windows is **Robocopy** (Robust File Copy). Unlike the standard copy command, it has specific flags for metadata.
+
+1. Open **Terminal** or **Command Prompt**.
+2. Use the following syntax:
+```cmd
+robocopy "C:\Source\Folder" "D:\Destination\Folder" /E /DCOPY:DAT /COPY:DAT
+
+```
+
+**Breakdown of Flags**
+
+* **`/E`**: Copies all subdirectories, including empty ones.
+* **`/DCOPY:DAT`**: This is the crucial part. It tells Windows to copy the **Data, Attributes, and Timestamps** for **directories**.
+* **`/COPY:DAT`**: Tells Windows to copy the **Data, Attributes, and Timestamps** for **files**.
+
+---
+
+#### 🍎 macOS: Using `cp` or `rsync`
+
+On macOS, the standard "Finder" copy usually preserves the *Modification Date* but often resets the *Creation Date* to the time of the copy. To preserve everything, use the Terminal.
+
+##### Option A: The `cp` command (Simplest)
+
+1. Open **Terminal**.
+2. Run:
+```bash
+cp -pPR /Source/Path /Destination/Path
+
+```
+
+
+
+* **`-p`**: Preserves modification time, access time, file flags, and permissions.
+* **`-R`**: Recursive (copies folders and their contents).
+
+##### Option B: `rsync` (Best for large transfers)
+
+Rsync is the professional standard for syncing data while maintaining metadata.
+
+```bash
+rsync -avz --times /Source/Path/ /Destination/Path/
+
+```
+
+* **`-a` (Archive mode)**: This is a "bundle" flag that preserves permissions, symlinks, and—crucially—timestamps.
+* **`--times`**: Explicitly ensures modification times are transferred.
 
 ## The shared data table