feat: add explanation of how date math works

src/i18n/lang/en.json

@@ -525,7 +525,38 @@
     },
     "datepickerRange": {
       "to": "To",
-      "from": "From"
+      "from": "From",
+      "math": {
+        "canuse": "You can use date math to filter for relative dates.",
+        "learnhow": "Check out how it works",
+        "title": "Date Math",
+        "intro": "Date Math allows you to specifiy relative dates which are resolved on the fly by Vikunja when applying the filter.",
+        "expression": "Each Date Math expression starts with an anchor date, which can either be {0}, or a date string ending with {1}. This anchor date can optionally be followed by one or more maths expressions.",
+        "similar": "These expressions are similar to the ones provided by {0} and {1}.",
+        "add1Day": "Add one day",
+        "minus1Day": "Subtract one day",
+        "roundDay": "Round down to the nearest day",
+        "supportedUnits": "Supported time units are:",
+        "someExamples": "Some examples of time expressions:",
+        "units": {
+          "seconds": "Seconds",
+          "minutes": "Minutes",
+          "hours": "Hours",
+          "days": "Days",
+          "weeks": "Weeks",
+          "months": "Months",
+          "years": "Years"
+        },
+        "examples": {
+          "now": "Right now",
+          "in24h": "In 24h",
+          "today": "Today at 00:00",
+          "beginningOfThisWeek": "The beginning of this week at 00:00",
+          "endOfThisWeek": "The end of this week",
+          "in30Days": "In 30 days",
+          "datePlusMonth": "{0} plus one month at 00:00 of that day"
+        }
+      }
     }
   },
   "task": {