Document year support for Arkane level of theory matching

Update the documentation to explain how to use the `year` attribute in `arkane_level_of_theory` for matching specific method variants in the Arkane database. This clarifies that year suffixes should not be included in standard quantum chemistry method definitions and describes the fallback logic used when a year is not explicitly provided.

Author: calvinp0

docs/source/advanced.rst

@@ -95,9 +95,19 @@ Another example::
 
 specifies ``DLPNO-CCSD(T)-F12/cc-pVTZ-F12`` model chemistry along with two auxiliary basis sets,
 ``aug-cc-pVTZ/C`` and ``cc-pVTZ-F12-CABS``, with ``TightOpt`` for a single point energy calculation.
+You can also provide a 4-digit ``year`` on ``arkane_level_of_theory`` to distinguish method variants
+in the Arkane database (e.g., ``b97d3`` vs ``b97d32023``)::
 
+    arkane_level_of_theory:
+      method: b97d3
+      basis: def2tzvp
+      year: 2023
 
-THe following are examples for **equivalent** definitions::
+If ``year`` is omitted, ARC will prefer the no-year Arkane entry for that method/basis. If none exists,
+ARC will fall back to the latest available year in the Arkane database.
+
+
+The following are examples for **equivalent** definitions::
 
     opt_level = 'apfd/def2tzvp'
     opt_level = {'method': 'apfd', 'basis': 'def2tzvp'}
@@ -138,6 +148,10 @@ is equivalent to::
     scan_level = {'method': 'wb97xd', 'basis': 'def2svp'}
     sp_level = {'method': 'wb97xd', 'basis': 'def2svp'}
 
+Note: Year suffixes in the method (e.g., ``wb97xd32023``) are meant for Arkane database matching
+and are not valid QC methods. Do not include year suffixes in ``level_of_theory``; instead, specify a
+``year`` key on ``arkane_level_of_theory`` if you need a specific correction year.
+
 Note: If ``level_of_theory`` does not contain any deliminator (neither ``//`` nor ``\/``), it is interpreted as a
 composite method.
 

docs/source/examples.rst

@@ -84,6 +84,13 @@ To specify a composite method, simply define something like::
 
     level_of_theory: CBS-QB3
 
+Note: Do not include year suffixes in ``level_of_theory`` (e.g., ``wb97xd32023``). Year suffixes are
+for Arkane database matching only and are not valid QC methods. If you need a specific correction year,
+specify a ``year`` key on ``arkane_level_of_theory``.
+
+If ``year`` is omitted, ARC will prefer the no-year Arkane entry for that method/basis; if none exists,
+ARC will fall back to the latest available year in the Arkane database.
+
 Note that for composite methods the ``freq_level`` and ``scan_level`` may have different
 default values than for non-composite methods (defined in settings.py). Note: an independent
 frequencies calculation job is automatically executed after a composite job just so that the Hamiltonian will