Two new cheats in date and ln sheets

cheat/cheatsheets/date

@@ -1,2 +1,5 @@
-# Printout date in format suitable for affixing to file names
+# Print date in format suitable for affixing to file names
 date +"%Y%m%d_%H%M%S"
+
+# Convert Unix timestamp to Date
+date -d @1440359821

cheat/cheatsheets/ln

@@ -1,2 +1,5 @@
 # To create a symlink:
 ln -s path/to/the/target/directory name-of-symlink
+
+# Symlink, while overwriting existing destination files
+ln -sf /some/dir/exec /usr/bin/exec